Allergen tests: how they do it. Skin tests for allergies - algorithm and results Skin tests show different results

Timely diagnosis of allergies is the main condition for its successful treatment and prevention of possible relapses. To carry it out, a comprehensive examination is carried out, an important component of which is allergy testing. Before the procedure, the doctor explains what allergen tests are, how they are done and how to prepare for them. However, it is advisable to study all the necessary information in more detail in order to obtain the most accurate test results and prevent complications from occurring.

Allergy tests are tests of the body to determine individual intolerance or hypersensitivity to specific irritants (allergens). Such an examination is necessary in the following cases:

if there is a tendency to allergic reactions, to identify most of the possible allergens;
at the slightest suspicion of an allergy before administering anesthesia, prescribing new medications, using unfamiliar cosmetics or other similar situations, especially in children;
if you need to identify an allergen, when the cause of a painful response immune system unknown to the patient.

In addition, some diseases are indications for testing:

bronchial asthma with severe respiratory disorders;
hay fever with pronounced symptoms of its classic manifestation;
food and drug allergies;
, conjunctivitis, dermatitis.

Allergy tests allow you to quickly obtain the necessary information about which substance causes increased sensitivity. To do this, the body is exposed to small doses of various irritants, and then the result is assessed by the nature of the reactions.

Diagnostic methods

The most reliable method for identifying allergens is a comprehensive allergy diagnosis using a blood test. It allows you to simultaneously determine the body's sensitivity to the 40 most common allergens different types. This method may be the only possible one if there are contraindications to skin testing, but it is very expensive and inoperative.

Faster and more accessible are skin and provocative tests, with which you can check the immune system's reaction to a maximum of 20 allergens.

Skin allergy tests are classified according to several criteria.

According to the final result:

qualitative – confirm or refute the presence of an allergy to a specific substance;
quantitative - determine the strength of the allergen’s impact and its critical amount that can cause negative reaction immune system.

According to the composition of the provoking substance used:

direct - carried out by applying or introducing pure allergen into the skin;
indirect (Praustnitz-Küstner reaction) - the subject is first injected with the blood serum of a person suffering from allergies, and a day later - the allergen.

By method of allergen administration:

application (patch tests) - to determine the majority of existing allergens;
scarification or needle (prick tests) – when seasonal allergies on plants, Quincke's edema, atopic dermatitis;
intradermal (injection) - to identify fungi or bacteria that have become the causative agent of allergies.

With any of these studies, some errors are possible due to external factors and characteristics of the body. To clarify the result if it does not coincide with the symptoms of the disease, provocative tests are additionally prescribed. They involve the direct impact of a provoking substance on the organ that has become the site of manifestation. allergic reaction.

The most commonly used tests are:

conjunctival (with allergic inflammations conjunctiva);
nasal (for similar inflammations of the nasal mucosa);
inhalation (for diagnosing bronchial asthma).

Other provocative allergy tests can also be performed - exposure or elimination (for food allergies), heat or cold (for a corresponding thermal rash), etc.

How are allergen tests done?

The procedure is performed by an allergist in a specially equipped room. He also evaluates the results obtained and makes an appropriate diagnosis.

Skin tests

Allergy tests of this type are carried out on healthy areas of the skin, most often in the forearm area, less often on the back. Each of the above procedures is performed in a special way:

Patch tests (patch tests) are performed using a gauze or cotton swab soaked in an allergen solution, which is attached to the skin using a patch.
Scarification or needle tests (prick tests) - involve the dropwise application of a provoking substance, followed by minor damage to the surface layer of the epidermis (light scratches with a scarifier or needle).
Intradermal tests (injections) are based on the administration of the drug by injection to a depth of no more than 1 mm. A white dense bubble with a diameter of about 5 mm immediately forms at the puncture site, which resolves within 15 minutes.

The results are assessed according to two parameters:

speed of reaction manifestation: instantly – positive; after 20 minutes – immediate; after 1–2 days – slow;
the size of the redness or swelling that appears: more than 13 mm – hyperergic; 8–12 mm – clearly positive; 3–7 mm – positive; 1–2 mm – doubtful; no change – negative.

The skin reaction is assessed on a scale from 0 (“–”) to 4 (“++++”), which reflects the degree of sensitivity of the body to the allergen.

Provocative tests

The methodology for conducting such studies depends on the location of the affected organ and the option of access to it:

Conjunctival test - carried out by first instilling a test control liquid into one eye, and if there are no changes within 20 minutes, then a minimal concentration of allergen solution is dripped into the other eye. If there is no reaction, after 20 minutes, the allergen solution is again instilled into the same eye, but with a concentration doubled. Such studies continue until there is no allergic reaction, constantly increasing the concentration by 2 times. Complete the test with undiluted allergen.
Inhalation test - carried out by inhaling an allergen aerosol in a minimum concentration, then the reaction is monitored for 1 hour (after 5, 10, 20, 30, 40 and 60 minutes) respiratory system. If there are no changes in the rhythm, depth and purity of breathing, the test is repeated again with a twice as high concentration of the allergen and is also brought to its undiluted state.
Nasal test - performed in a similar way, but the corresponding liquids are instilled into one and the other halves of the nose.

An exposure test involves direct exposure to a possible irritant and is performed in cases where there are no pronounced manifestations of an allergic reaction. Elimination tests are also performed in the absence of symptoms, but using the reverse method - by refusing to consume a possible allergen product, changing the environment, discontinuing the drug, etc.

When choosing an allergen test option, it is necessary to consider all the pros and cons of each of them. Skin tests are fairly quick and simple, but are unsafe as they can aggravate allergies. It is also possible to obtain false results, which largely depend on the condition of the skin, the subjectivity of the assessment, and technical errors. In addition, such allergy tests have a number of contraindications.

Contraindications for staging

All types of allergy tests are not performed in the following cases:

exacerbation of allergies and for 2–3 weeks after it;
reception antihistamines and other drugs that suppress the production of histamine, and the first week after their withdrawal;
use of sedatives and other sedatives containing barbiturates, bromine and magnesium salts, and 7 days after stopping use;
exacerbation of chronic diseases, including neuropsychiatric disorders, or the recovery stage;
bearing and feeding a child, menstruation - in women;
previous history of anaphylactic shock;
taking hormonal drugs and 2 weeks after completion of the course;
presence of infectious and inflammatory processes in the body (respiratory, viral diseases, sore throat, etc.), as well as intercurrent infections;
cancer, AIDS, diabetes mellitus;
the presence of an acute reaction to a specific allergen;
age up to 3–5 and after 60 years.

If there is any contraindication to skin testing, allergy diagnosis is performed based on a blood test.

Complications of allergen testing

The most serious complication after allergy testing can be caused by delayed-type hypersensitivity, which develops within 6-24 hours after the test. Its manifestations can be expressed by the following symptoms:

deterioration of health, the appearance of discomfort;
irritation and prolonged non-healing of the allergen injection site;
development of increased sensitization to the irritant or a new allergic reaction.

In some cases, on the contrary, there is no skin reaction, which does not allow identifying a specific allergen and obtaining a specific result from the test performed. Hypersensitivity to the test itself may also occur, the consequences of which can be unpredictable and very dangerous, including death.

How to prepare for tests

Preparation for testing for allergens should begin with an analysis of contraindications and the exclusion of all possible factors that could distort test results. It should also be taken into account that tests can only be carried out during stable remission, at least a month after an exacerbation.

Besides, preparatory stage includes the following restrictions:

3 days before the examination you need to reduce physical activity;
1 day in advance - quit smoking;
on the day of testing - do not eat food, since skin tests are performed on an empty stomach or at least 3 hours after eating.

If you are prone to allergies, you need to take tests for allergens at least once in your life, as people who care about their health do. It is always easier to prevent any disease than to then eliminate its symptoms and consequences. This is especially important in cases of allergic reactions. After all, they can arise from completely unexpected irritants, knowing which, you can avoid contact with them and live your whole life without allergies.

Skin testing for allergens is one of the main ways to diagnose allergic diseases. The results obtained after a skin test allow the doctor to develop a treatment plan and the patient to avoid allergens in the future. In this article we will look at what an allergy examination is and how an allergy test is done for children and adults.

What are allergy tests?

Allergy tests on the skin are the most well-known diagnostic method for determining substances to which a person exhibits an increased reaction of the body. Their popularity is explained by the fact that they are carried out almost painlessly and cover wide range allergens, especially those related to airborne substances: pollen, animal dander, dust mites. There is also a test for food allergens, but it often requires additional diagnostic methods.

Skin tests for allergens: types

Scarification test

A scarification allergy test consists of incisions on the skin of the forearm, through which the expected antigen, in the form of a solution, easily penetrates the human body.

This type of study allows you to check for respiratory and household allergens.

Prick test for allergens

Prick allergy tests are performed by introducing an antigen under the patient’s skin, that is, they represent a kind of injection. A typical testing area is the skin of the forearm, less often the back.

It is worth noting that intradermal tests are more sensitive than prick tests.

This allergy test allows you to identify sensitivity to insect venom, antibiotics and is not used to diagnose food allergies due to high risks false positive results and the risk of anaphylaxis.

Allergy patch tests (patch test)

This allergy test involves applying antigen-treated patches to the skin of the back for 48 hours. This examination is carried out to identify delayed-type allergies. That is, reactions that occur after several hours or days after skin contact with an allergen are tested, for example, contact dermatitis.

The patch test allows you to check your reaction to latex, metals, fragrances, medications, preservatives, resins, hair dyes, etc.

Provocative tests in allergology

Oral or nasal allergy provocation tests are performed when there is a suspicion that a person has an allergic reaction to food or medications.

The procedure is carried out as follows: the suspected allergen, starting with very small doses, is eaten or inhaled under the close supervision of an allergist. If there is no reaction, the dose is increased until the body shows a positive response to the antigen.

Rinse test

This procedure involves the diagnosis of food or drug intolerance, used for both true and false allergies.

After contact of the antigen with the oral mucosa, the number of leukocytes is assessed. Sensitivity to the substance causes inhibition of neutrophil emigration, which indicates the presence of an allergy.

Allergy tests at home

Do not attempt allergy tests at home. Self-administered food allergy testing may cause anaphylaxis, a reaction life threatening. Testing for drug allergies should also be carried out only in medical institution under the supervision of a highly qualified specialist who can provide emergency assistance if the test progresses unfavorably.

Blood test for allergens

In the event that a person exhibits any kind of allergy, tests are not the only method used in medicine to diagnose the disease. If a person is unable to undergo testing due to age or his disease is in the acute stage, you can always use alternative method diagnostics and allergy testing.

You can take allergy tests using this method at any time of the year, without waiting for remission of the disease, unlike classical diagnostics.

You can donate blood for allergy tests at a specialized medical center. The advantage of this method is that it is not able to provoke anaphylaxis, and taking antihistamines does not affect the result.

Blood tests for allergies are called allergy screening. This is a test in which total or specific Immunoglobulin E (IgE) is determined.

Immunoglobulin E (IgE) is a class of antibodies (immune proteins) associated with allergic reactions. In a healthy person, they are contained in the blood in small quantities, but when an allergy occurs, their number can increase many times over.

An analysis for total IgE shows the amount of antibodies present in the blood, that is, it informs the doctor whether a person really has an allergy or whether the symptoms that have arisen are signs of another disease.

In order to identify a reaction to a specific allergen, a blood test is performed for specific Immunoglobulin E (PACT allergy test). With this testing, it is possible to determine sensitivity to respiratory, food, drug, mold, household and other antigens.

The disadvantages of this testing include the cost and waiting for results within several days.

Allergy panels: types

Today, blood allergy tests can be tested immediately for a complex of a wide range of antigens, which is an allergy panel. For the convenience of the patient, depending on the laboratory, the following types of allergy panels may be offered:

food (vegetables, fruits, spices, additives, etc.);
respiratory (pollen, mold fungi, dust, household allergens, etc.);
mixed (food and inhalation antigens);
pediatric (the most relevant allergens found in pediatrics);
pre-vaccination (allergens included in vaccines);
preoperative (anesthetics, latex, formaldehyde, etc.);
diagnosis of a specific disease (asthma, rhinitis, eczema, etc.).

Where can I get allergy tests done?

Allergy tests can be done free of charge at the clinic at your place of residence, having previously received a referral from a therapist. You can also take allergy tests at private medical centers that have an allergist on staff. The cost of research on average is 300 - 600 rubles per allergen.

Preparing for allergy tests

In order to get a reliable result, you should properly prepare for allergy tests.

Two weeks before the designated date of the study, you must stop taking antihistamines.
A few days before the procedure, alcohol consumption is not allowed, and the intake of fatty and fried foods is reduced.
On the eve of the study, you should measure your body temperature and make sure that you are feeling normal.
Regarding blood collection: it is done on an empty stomach. Food should be consumed no more than 8 hours before the test. IN otherwise, the result of the test may be false.

How are allergy tests taken?

Many people have no idea how allergy testing is done. Below we will consider the main testing methods that exist today.

Skin tests for allergies are carried out in different ways, depending on the method of diagnosis.

Scarification test. This type of testing uses needles (lancets) that lightly damage the surface of the skin. However, the discomfort is so minimal that the tests can be easily tolerated even by small children.

The process of taking an allergy test is as follows: after cleaning the test area with alcohol, the doctor makes marks on the skin with a marker, then, next to each mark, creates a minor scratch and drips the allergen extract on top of it. At the same time, each new substance uses its own lancet. The procedure takes about 30 minutes.

In order to assess how adequately the skin reacts to the tested substances, two additional agents are applied to the surface:

Histamine, which in most cases causes a reaction to it. If there is no reaction, this may indicate that the test may not detect an allergy, even if the person actually has one.

Glycerin or saline solution. As a rule, they should not cause any reaction. However, if a person reacts to these substances, this indicates increased skin sensitivity. Therefore, test results must be interpreted with caution to avoid misdiagnosis of allergies.

Prick test is carried out as follows: a solution containing a suspicious allergen is applied to the skin of the forearm in the form of drops, which are then pierced with a special needle, thereby allowing them to penetrate the body. After 10-15 minutes, the doctor notes the reaction of the immune system to the antigen.

Patch tests do not involve the use of needles. Instead, allergens are applied to patches that are placed on the back for 48 hours. During this time, you should avoid swimming and activities that cause sweating.

How are allergy tests done for children?

Many parents are interested in the question of how to check for allergies in their child? In general, allergy skin tests in children are carried out in the same way as in adults. Only provided that the child is 5 years old at the time of the procedure.

Early childhood is a contraindication for testing because the child’s immunity before this age is not yet fully formed. In addition, it will be difficult for the baby to endure this rather lengthy process.

The most common allergy test for children is a blood test for specific IgE.

You can find out what exactly the child is allergic to by taking a test for specific Immunoglobulin E. In this case, the child’s blood is taken and tested for sensitivity to any allergens, regardless of the stage of the disease and the time of year.

Indications for allergy testing

Allergy testing is prescribed to make a correct diagnosis and determine further treatment, which includes limiting contact with the allergen, following a hypoallergenic diet, or replacing a medication that causes an increased reaction of the body.

As a rule, allergy tests are performed if a person has:

allergic rhinitis (hay fever);
allergic asthma;
eczema, dermatitis of various etiologies;
allergies to food, insect venom, mold, inhalation antigens, penicillin or other drugs.

Contraindications for allergen testing

Taking antihistamines or psychotropic medications, such as antidepressants or antipsychotics, a few days before the procedure, may give false positive results. negative result. And beta blockers can increase sensitivity to allergens and increase allergic reactions. Therefore, before allergy testing, it is necessary to consult with your doctor and allergist.
Allergy skin tests are performed only if the testing area is healthy, that is, the person does not have eczema or other skin lesions.
Viral infection (ARVI), stress, oncology, pregnancy, autoimmune diseases, diabetes, exacerbation of allergies are also contraindications.
Allergy tests are carried out only in late autumn or winter, when the disease is in remission.
Allergy tests also have age restrictions: children under 5 years of age and elderly people over 60 years of age can only be tested for an allergic reaction by taking a blood test.

Side effects

Most common side effects– this is redness, swelling and itching at the site where the integrity of the skin is broken. As a rule, these symptoms disappear a few hours after the procedure.

With the correct approach to the test, serious immediate allergic reactions occur in exceptional cases and can be treated with medications available in the doctor’s office.

Skin allergy tests: explanation

An allergen test is considered positive if redness and slight swelling of the skin occurs at the site of a scratch or puncture, as well as when an itchy blister with a diameter of 5 mm or more forms.

Photo: positive allergen test result

Deciphering the skin test for allergens

Interpretation of the scarification allergy test

Interpretation of intradermal allergy test

Interpretation of a blood test for allergies

Interpretation of blood test results should only be carried out by an allergist, since reference values may vary depending on the laboratory.

Normal level Immunoglobulin E in blood serum.

Increased levels of Immunoglobulin E with pathological conditions.

Now you know what allergy tests are, when it is best to do them and how to decipher them. We wish you good health!

Allergy tests (or allergy tests) are diagnostic techniques for identifying individual intolerance to various substances (i.e., allergens). Their appointment can significantly help in eliminating the allergic reaction and allows you to determine the maximum number of allergens. This article provides information on methods, indications, contraindications, methods of preparing and passing allergen tests. The data obtained will allow you to get an idea of such diagnostic techniques, and you will be able to ask your attending physician any questions you may have.

Such tests are recommended by experts to every allergy sufferer, since the tests make it possible to create a so-called black list of those irritants that unbalance the immune system. The results of allergy tests allow you to exclude contact with allergens, create the necessary diet and prescribe the most effective treatment.

Indications

Occurs frequently, not associated with viral diseases Nasal congestion is an indication for allergy testing.

In some cases, it is impossible to determine the type of allergen through normal observation of diet and environmental factors. In such situations, the doctor recommends allergy tests using one or another method. The following patient complaints may be indications for such studies:

unreasonable frequent nasal congestion and discharge from it;
gratuitous or nasal;
constant presence on the body, accompanied by itching;
swelling of the skin;
sudden attacks of suffocation, wheezing, shortness of breath, difficulty breathing, or a suffocating cough;
the appearance of an allergic reaction to (itching, redness, swelling of the skin, rash, difficulty breathing).

Some experts recommend conducting allergy tests for periodic dyspeptic disorders (vomiting and stomach pain) or dry skin. Their implementation makes it possible to exclude or confirm the presence of allergic reactions and can be a differential diagnostic method for other diseases with similar symptoms.

All of the above symptoms may indicate the presence of the following allergic reactions:

and/or conjunctivitis;
(rash, itchy skin, dyspepsia);
allergies to medications.

The main purposes of prescribing allergy tests

The purposes of prescribing allergen tests are aimed at:

eliminating the allergen or prescribing effective treatment;
identifying an allergic reaction to a cosmetic product or household chemical;
testing of new prescribed drugs.

Tests to identify individual intolerance to drugs or household chemicals and cosmetics help prevent the development of an allergic reaction, and tests to identify an allergen help to identify not only suspected irritants, but also identify unknown substances that can provoke allergies. Performing such tests allows you to choose a way to combat allergies:

Complete elimination of contact with the allergen is the most effective method, but not always possible;
the appointment of SIT (specific immunotherapy with allergens) is the most effective way treatment, but requires systematic annual repetition of courses for 3-4 years;
Symptomatic therapy does not cure allergies, but helps eliminate its symptoms.

Types of allergy tests

There are many methods for performing allergy tests. One or more of them can be used for diagnosis.

Most often, allergy patients are prescribed the following two types of tests:

comprehensive allergy test using immunological blood tests;
skin allergy tests.

In more rare cases, provocative tests are performed.

Immunological blood tests

Such allergy tests make it possible to detect the presence of an allergic reaction even to early stages its manifestations and identify allergens. For this purpose, the following methods can be prescribed:

analysis for total immunoglobulin E (IgE);
tests for specific immunoglobulin E (IgE);
ImmunoCap tests.

The principle of these laboratory research is based on identifying in the blood and determining the level of antibodies - immunoglobulins E and G, formed in response to exposure to allergens.

Test for total IgE

Such immunological tests blood tests are prescribed for children or adults if the following diseases are suspected:

bronchial asthma;
bronchopulmonary aspergillosis;
dermatitis;
individual intolerance to certain foods;
individual intolerance of some medicines etc.

In addition, such an analysis can be prescribed to children whose parents are prone to allergic reactions.

Blood is drawn from a vein after the necessary preparation:

Tell your doctor about all medications you are taking.
A few days before donating blood, stop eating highly allergenic foods (eggs, chocolate, strawberries, etc.), alcoholic beverages, fatty and spicy foods.
3 days before the study, all physical and psycho-emotional stress is excluded.
In the morning before blood sampling, you should not drink or eat.
Stop smoking an hour before the test.

If the test results for total IgE reveal an increase in its level, this indicates the presence of an allergic reaction.

Normal levels of IgE in the blood:

children from 5 days to 1 year – 0-15 kU/ml;
children from 1 to 6 years old – 0-60 kU/ml;
children from 6 to 10 years old – 0-90 kU/ml;
children from 10 to 16 years old – 0-200 kU/ml;
over 16 years old and adults – 0-100 kU/ml.

Analysis for specific IgE and IgG4

The level of immunoglobulins is determined in the patient’s blood taken from a vein.

This test identifies one or more allergens that cause an allergic reaction. This laboratory diagnostic method is prescribed to people of any age for:

the impossibility of determining the factor that provokes the allergy based on observations and clinical picture;
widespread dermatitis;
the need to establish a quantitative assessment of sensitivity to an intolerable substance.

The principle of performing such an immunological allergy test is to mix samples of serum obtained from blood with allergens (for example, pollen, animal dander, household dust, detergents etc.). The results of the analysis can be demonstrated by reagents: enzymes (for the ELISA test) or radioisotopes (for the RAST test). To carry out the analysis, blood is donated from a vein on an empty stomach, and the principle of preparing for the study is similar to preparing for donating blood for total IgE.

This technique for identifying allergens is completely safe for the patient, since he does not come into direct contact with causing allergies substance and does not receive additional sensitization. The following basic allergen panels can be used for analysis:

allergy screening for 36 allergens: hazel pollen, white birch, Kladosporium and Aspergillus mushrooms, black alder, quinoa, fescue, dandelion, rye, wormwood, timothy, bird feathers (mixture), horse, cat and dog hair, household dust, cockroach, mixture cereals (corn, rice and oats), beef, chicken eggs, chicken meat, pork, tomato, carrots, strawberries, apples, cod, cow's milk, potatoes, hazelnuts, soybeans, peas, wheat;
allergy screening for 20 allergens: ragweed, wormwood, white birch, timothy, Kladosporium, Alternaha and Aspergillus mushrooms, D. Farinae mite, D. Pterony mite, latex, cod, milk, egg white, soy, peanuts, wheat, rice, cat hair , dogs and horses, cockroaches;
IgE food panel for 36 food allergens: white beans, potatoes, banana, orange, raisins, mushrooms, cabbage mix (cauliflower, cabbage and broccoli), celery, wheat, carrots, garlic, almonds, peanuts, walnuts, chicken, beef, turkey, egg whites, egg yolks, pork , cod, tuna, cow's milk, onion mixture (yellow and white), yeast, soy, rye, tomatoes, rice, pumpkin, seafood mixture (shrimp, mussels, crab), chocolate.

There are many different allergy panels, and the choice of one or another technique is determined by the doctor individually. In some cases, the patient may be recommended to donate blood to a list of allergens determined by a specialist individually (the so-called in-depth allergy screening), a fungal panel (includes about 20 of the most common molds), a card of alcohol allergens or a MIX panel (for 100 allergens).

The results of the analysis for specific IgE and IgG4 reflect the sensitivity to a particular allergen in the panel:

up to 50 U/ml – negative;
50-100 U/ml – low sensitivity;
100-200 U/ml – moderate sensitivity;
above 200 U/ml – high sensitivity.

The duration of the tests can be several days (depending on the laboratory).

ImmunoCap tests

In the most difficult diagnostic cases, patients suffering from allergies may be recommended to undergo ImmunoCap tests. These methods allow not only to determine the intolerable substance, but also to identify the presence of a cross-reaction between different types of molecules and “calculate” the most major (i.e., malicious) allergen.

Preparation for performing such tests is similar to the procedure for preparing for analysis for total IgE. However, to perform it, it is necessary to take a larger volume of blood, which precludes the use of this method for examining infants.

When prescribing an ImmunoCAP test, a patient may be recommended one or more allergy panels:

pollen;
food;
mite allergens;
tick;
inhalation Phadiatop;
food fx 5;
polynosis MIX;
timothy grass (mixture);
timothy, wormwood, ragweed;
early spring herbal mixture;
atopy MIX;
fungal molecular 1 or 2;
ambrosia;
household;
autumn-wormwood.

The duration of the tests can be about 3 days (depending on the laboratory).

Skin allergy tests

An allergy skin test involves applying allergens to the skin and then assessing the skin's reaction to each substance.

Such allergy tests will allow you to quickly identify hypersensitivity to various substances by applying them to the skin and assessing the intensity of the inflammatory skin reaction. Sometimes such tests are performed to identify certain infectious diseases– tuberculosis and brucellosis.

In one day, 15-20 skin allergy tests with different allergens can be performed. A 5-year-old child can be tested with only two drugs at a time. Such tests can be carried out on adults up to 60 years of age, and they are prescribed to children only after reaching 3-5 years of age.

The following types of skin allergy tests can be used for diagnosis:

qualitative (or prick tests) - detect an allergic reaction to a certain substance;
quantitative (or allergometric testing) - determine the strength of the allergen and indicate the amount of intolerable substance that causes an allergic reaction.

Typically, such tests are performed on the flexor surfaces of the forearms, and in some cases on the back.

Before performing such allergy tests, the patient is recommended to prepare for the study:

Tell your doctor about all medications you take and previous illnesses.
14 days before the tests, stop taking glucocorticosteroids (internally and externally).
Stop taking it 7 days before the test.
Have a snack before performing the study.

High-quality skin allergy tests can be performed using the following methods:

drip – a drop of the allergen is applied to the skin and the result is assessed after a certain time (performed only for small children);
application - pieces of fabric soaked in the allergen are applied to the skin;
scarification - scratches or micropunctures are made on the skin with a needle or scarifier, onto which the allergen is applied;
injection - intradermal injections are performed using an insulin syringe with an allergen solution.

Most often, the scarification method is performed. The study is carried out in a specialized department of the clinic, where, if necessary, the patient can receive urgent Care, or in a hospital.

To perform skin tests, different lists of allergens are used:

household: daphnia, library dust, house dust mites, etc.;
pollen: hazel, birch, alder;
meadow and cereal grasses: timothy, cocksfoot, rye, oats, etc.;
weeds: ragweed, nettle, wormwood, white pigweed, dandelion, etc.;
fungi: mold, etc.;
epidermal: rabbits, cats, dogs, mice, parrots, horses, rats, etc.

Methodology for performing a high-quality allergy test:

The skin is treated with alcohol.
After drying, allergens are marked on the skin (by number) using a hypoallergenic marker.
A drop of the corresponding allergen (or pieces of tissue soaked in the allergen during an application test) is applied near the marks.
On separate plot a neutral test control solution is applied.
When performing a scarification test, small scratches (up to 5 mm) or punctures (no more than 1 mm) are made with a needle or scarifier. A separate needle or scarifier is used for each drop of allergen.
The doctor begins to monitor the condition of the skin and general condition patient.
The final assessment of results is performed after 20 minutes and 24-48 hours.

The rate of onset of an allergic reaction is assessed by the following indicators of the appearance of redness or a blister:

instantly – positive reaction;
after 20 minutes – immediate reaction;
after 24-48 hours – slow reaction.

In addition, the skin reaction is assessed on a scale from “-” to “++++”, which reflects the degree of sensitivity to the allergen.

After completion of the study, the patient must be under medical supervision for 1 hour.

What may affect the reliability of the results?

In some cases, allergy skin tests may give false or false-positive results:

improper execution of skin scratches;
decreased skin reaction;
taking medications that can reduce the rate of an allergic reaction;
improper storage of allergen solutions;
allergen concentration is too low;
too close location of skin scratches (less than 2 cm).

Provocative tests

Provocative tests for exposure to allergens are performed in rare cases. They can be prescribed only when all other allergy tests “do not work” and signs of an allergic reaction remain. The principle of their implementation is based on the introduction of an allergen to the place where signs of the disease clearly appear.

Provocative tests are as follows:

conjunctival - used to identify allergic conjunctivitis by injecting an allergen solution into the lower conjunctival sac;
inhalation - used to detect bronchial asthma by introducing an aerosol of an allergen into the respiratory tract;
endonasal - used to identify allergic rhinitis or polynosis by instilling an allergen solution into the nasal cavity;
temperature (cold or heat) - used to identify thermal or cold urticaria by performing a particular temperature load on a certain area of the skin;
elimination – consist in completely limiting the patient from food or drug allergens;
exposure – consist of ensuring direct contact of the patient with the suspected allergen;
thrombocytopenic and leukocytopenic - involve the introduction of a food or drug allergen and after some time performing an analysis of the level of leukocytes and platelets in the blood.

Such tests can only be carried out in a hospital setting, and solutions of these substances in a dilution of 1:1000 are used as an allergen.

Contraindications to allergy tests using allergens

In some cases, performing any tests using allergens is contraindicated:

taking antihistamines (Diazolin, Tavegil, Loratadine, Zyrtec, Erius, etc.) - an allergen test can be carried out only a week after their discontinuation;
occurrence of acute or exacerbation chronic disease– the study can be performed in 2-3 weeks;
exacerbation of allergies - the test can be performed 2-3 weeks after the cessation of all symptoms;
reception sedatives(valerian, motherwort, Persen, Novo-passit, bromine salts, magnesium, etc.) - analysis can be performed 5-7 days after their discontinuation;
taking glucocorticoids - the test can be carried out 2 weeks after their discontinuation;
a history of anaphylactic shock;
period of menstruation, pregnancy or lactation;
and other immunodeficiencies;
intense acute reaction to an allergen;
autoimmune diseases;
mental disorders, some diseases nervous system, convulsions;
severe course

Skin allergy tests are a diagnostic method for identifying specific sensitization of the body by introducing an allergen through the skin and assessing the magnitude and nature of the swelling or inflammatory reaction that develops. Skin tests (ST) are usually performed during the period of remission. There are qualitative and quantitative, direct and passive skin tests.

Quantitative tests give an idea of the degree of sensitization. They are placed to identify individual sensitivity and resolve the issue of initial doses of the allergen when carrying out specific hyposensitization.

In direct skin allergy tests, the allergen is administered to the patient being studied. With passive or indirect skin allergy tests, the patient’s blood serum is injected intradermally into a healthy person, and then the allergen is injected into the injection sites of the serum (Prausnitz-Küstner reaction).

The time at which a skin reaction appears after exposure to an allergen and its nature depend on the type of allergic reaction. With the reagin type, the reaction appears in the first 10-20 minutes. It is a round or irregular blister with pseudopodia. The color of the blister is pinkish or pale with an area of arterial hyperemia around it. Its development is based on acutely developing limited swelling of the papillary layer of the skin due to increased vascular permeability. This reaction is called a wheal, urticarial or immediate type reaction. In allergic processes of types III and IV, the skin reaction is acute inflammation with all its signs - redness, swelling, increased temperature in the area of inflammation and pain. The difference between type III and IV lies in the time of development and intensity of inflammation. At III type inflammation is more pronounced, it appears after 4-6 hours and goes away after 12-24 hours. With type IV, inflammation reaches maximum development after 24-48 hours. Thus, using skin allergy tests, you can determine the type of allergic reaction to a given allergen.

Depending on the specifics of the case, various methods of performing skin allergy tests are used. The choice of method depends on:

type of disease;
expected type of allergic reaction;
the presumed group affiliation of the allergen.

Contraindications

There are age restrictions for both adults and children. People over 60 years of age and children under three cannot undergo allergy testing. There are contraindications for women as well.
Tests are not carried out on pregnant and breastfeeding mothers, you should also not come for the allergen identification procedure in the first days of menstruation.
Testing cannot be performed if the patient is taking glucocorticosteroids or other hormonal drugs. It is recommended to do tests 2-3 weeks after stopping these medications.

People who have had it at least once are never tested. Testing should not be performed on patients suffering from diseases such as AIDS, diabetes mellitus, mental disorders and oncology.

Types of allergy tests

Before performing tests, an allergist must analyze the body’s previous reactions and determine the group of allergens that will be used for testing.

The procedure is carried out taking into account the patient’s age, heredity, and the seasonality of the disease. For the adult population, professional activities are also taken into account.

All samples can be divided into the following categories:

Allergy tests by blood

Blood from a vein is taken for analysis to find out what antibodies are present in a person. Usually they take a test for immunoglobulins E and G. Performed this procedure, if other allergy tests cannot be done for any reason. In this case, you need to prepare for the blood drawing procedure.

You should limit yourself in physical activity, follow a diet for at least three days, in which you are prohibited from eating fried, fatty foods, as well as foods that can cause. A complete cessation of alcohol and smoking is required. The analysis is carried out on an empty stomach.

It is prescribed for the following diseases:

dermatitis and eczema;
bronchial asthma.

Skin tests

Skin tests for allergies involve the introduction of a certain dose of a substance (allergic irritant) that shows the human body’s susceptibility to it.

Testing can be qualitative (the type of allergen is determined) and quantitative (shows a person’s sensitivity to the dose received). No more than 15-20 allergy tests should be performed at a time. For small children at the age of 5, 2-3 tests are done.

Scarification test, or prick test, considered the most common verification method. The suspected allergens are applied in a minimal dosage to the forearm, which is previously cleaned, and small incisions are made on the skin at the site of application using a special device - a scarifier. Scarification tests are recommended for severe manifestations of dermatitis, Quincke's edema, bronchial asthma. The accuracy of this method is 85%.
Skin test, or applique, It is most often performed on the back and is done in the form of attaching strips with a liquid allergen, which is covered with a film and secured with a band-aid. It is carried out for various types of dermatitis. Examine the results of the reaction to skin after 20 minutes, after 5 hours of exposure, and also after a day.
Intradermal tests done in rare situations. The method consists of introducing an allergenic irritant under the skin. This test is performed to determine allergies of fungal or bacterial origin.

Provocative tests

The study of allergic reactions using provocative tests involves influencing directly the organ that suffers most from negative symptoms.

This technique for identifying an allergen is more accurate compared to skin tests. But it is carried out extremely rarely, only when the irritant cannot be identified by any other means.

Nasal test performed using a special inhaler. It contains the intended irritant. It is administered through the nasal passage by spraying onto the mucous membrane. If no reaction is observed, then the procedure is repeated with increasing concentration of the allergen. The repetition can be carried out up to 10 times. If after this no reaction is detected, then the sample is considered negative.
Conjunctival test is based on the introduction of physiological fluid into one eye, after which, after 1/3 of an hour, the allergen with the maximum allowable dosage is dripped into the second eye. If a reaction is detected, the sample is counted as positive. This test cannot be performed if the mucous membrane of the eye is inflamed or if the eyelids are inflamed.
Inhalation test rarely carried out. Its use makes it possible to identify the allergen that affects the appearance of bronchospasms. The patient inhales an aerosol with a minimal dosage of the allergen. The procedure is repeated 5 times within an hour at intervals of 10-15 minutes. If a reaction is not noticed, then testing is repeated with an increased dose of the allergen.

Specifics of testing

Any testing to identify an allergen must be subject to the following conditions:

Performed strictly on an empty stomach.
Tests must be carried out in a medical institution and only by medical specialists.
The room where samples are taken must have facilities available to assist with unpredictable reactions. Application of samples must be carried out in the presence of a doctor. Even a minimal dose of an introduced allergen can cause a response from the body in the form of Quincke's edema.
The test can be carried out only when at least 2-3 weeks have passed since the last exacerbation. Also, the patient should not suffer from colds and infectious diseases.
The day before testing, you must stop taking any antihistamines in order to obtain a reliable result.

Features of testing in children

Before testing, parents should prepare their child for this procedure. Before testing you must pass clinical analysis blood and urine.

Testing for allergens in children has its own characteristics. IN childhood are often vaccinated against various diseases. Allergy testing can only be done 3 months after the next vaccination.

A doctor can prescribe allergy tests for children as a preventive measure. if immediate family members suffer from a severe allergic reaction. This should be done in order to establish the possibility of an allergic reaction of the body to initial stage to prevent its development. For example, if a mother has hay fever, the likelihood that the child will suffer from the same disease increases to 75%.

An allergist must determine what form of allergy the child has. The choice of testing method will depend on this, as well as at what age this procedure can be done. It is recommended that children with the passive form be tested no earlier than 5 years of age, since at this stage the body can cope with allergies on its own. For special indications, tests may be prescribed at the age of 3-4 years.

In children, the allergen is usually detected through skin testing.

Sample evaluation

After testing, it is important to correctly evaluate the results obtained. The doctor evaluates the samples based on reaction speed. If the skin at the site of allergen injection turns red, blisters, or swells during the first hour of examination, then the reaction is considered immediate and the test is positive. If a reaction to the injected allergen occurs within a day, the test result is considered weakly positive.

The reaction is also assessed by measuring the amount of redness of the skin:

no changes are observed - negative test;
up to 3 mm – questionable reaction;
over 3 mm – positive reaction.

Most often, allergies are associated with a disorder of the immune system. Therefore, if any type of allergic reaction is detected, measures should be taken to strengthen the immune system.

Available various techniques conducting allergy tests. The allergist must determine which method of identifying the allergen should be chosen. The choice of method is influenced by factors such as age, heredity, type of allergic reaction, and seasonality of its manifestation. Once the irritant is identified, the patient will be able to avoid contact with it, which will help maintain his health.