Skin tests as a diagnostic method

An allergic reaction has many manifestations, and we all know them well: rhinitis, lacrimation, itching, rash, redness, cough, swelling of mucous membranes, nausea, and many others. Moreover, the manifestations of an allergy to the same substance in different people may differ not only in the intensity of the reaction - the symptoms themselves may be different (for example, one with an allergy to eggs starts vomiting, and the other has a skin rash). At the same time, different types of allergic reactions can have similar symptoms. So how do you understand which specific allergen the immune system reacted to? One of the diagnostic methods that can answer this question are skin tests, which will be discussed in this article.

Anyone who has experienced an allergic reaction should visit an allergist. Only a specialist will be able to determine with maximum accuracy which substance caused the immune response. Diagnosis includes a number of activities: a detailed survey of the patient, skin allergy tests, a blood test for the level of immunoglobulin E, a blood test for allergens, provocative tests. Such an integrated approach allows you to reliably identify the allergen and select an effective treatment regimen.

Indications for appointment

The doctor may prescribe an allergy test on the skin if the patient has the following indications:

• hay fever (reaction to plant pollen);
• allergic contact dermatitis ;
• asthma attacks provoked by the ingestion of an allergen by the respiratory route;
• food allergy;
• drug allergy.

And this is not the whole list. The decision to conduct an allergy test is made by the doctor, evaluating each specific case.

Types of analysis

In the arsenal of modern medicine, there are several types of skin allergy tests:

1. Scarification tests.
2. Prick tests.
3. Application tests.
4. Subcutaneous tests.

Each of these varieties has its own advantages and characteristics, and each of them is highly informative (provided that it is properly prepared and carried out).

Scarification method

Skin tests for allergens often imply the scarification method of conducting. essence is that solutions of alleged allergens are dripped onto the skin of the forearm, previously cleansed with alcohol. Then, with a special scarifier (a sterile disposable blade), the surface of the skin is scratched under a drop. In order to avoid an erroneous result, each allergy test is mandatory signed. The first results are evaluated already after 15-20 minutes: redness, swelling, itching appear in the places of application of allergens that cause an immediate immune response. If the size of the papule is 2 mm or more, the reaction to the sample is considered positive. The final conclusions about the reaction to allergens are made after 48 hours after application. During this period, it is forbidden to wet, scratch, rub the site of application of skin tests.

Prick tests

The prick test is a variation of the scarification method. The difference is that the skin under a drop containing the allergen is pierced with the finest needle. As with the scratch test, the final result is evaluated after 48 hours.

Application method

contact dermatitis is suspected in order to accurately determine the substance, contact with which caused an allergic reaction. Unlike scarification methods, the skin is not injured. Solutions with allergens are applied to cotton or gauze swabs and fixed in most cases on the back in the interscapular zone. Each allergen must be signed. The first results may also appear within half an hour (in case of an immediate immune reaction to the allergen). Allergy tests are removed from the skin after two days. During this time, the place of application must be protected from moisture (it is also impossible to sweat), friction, direct sunlight, hypothermia. The result is considered positive when redness, blisters, rashes appear at the points of contact with the allergen.

Subcutaneous method

With the subcutaneous diagnostic method, the allergen solution is injected directly under the skin, shallowly (as in the Mantoux reaction). Otherwise, the procedure does not differ from other types of allergy tests.

Skin tests of all types are united by a general rule: no more than 15-20 allergens are applied in one procedure. Also, in parallel with allergens, the doctor can apply saline and histamine solution. The reaction to histamine gives out its presence in the blood at the time of the analysis, which means that the results of the study cannot be considered absolute and it is necessary to additionally conduct a blood test for allergens.

Depending on the result, which is classified according to the severity of the reaction (positive, weakly positive, negative or doubtful), the doctor decides on the need for additional studies.

Contraindications

Allergy skin tests are a relatively safe method of diagnosis. However, due to the fact that in very rare cases, the reaction to the allergen can be quite strong (up to the development of anaphylactic shock ), all procedures are carried out strictly in a hospital under the supervision of doctors. Allergy testing is contraindicated in the following cases:

• children's age up to 5 years;
• pregnancy;
• lactation period;
• exacerbation of chronic diseases of any organs;
• acute infectious diseases;
• age over 60;
• hormone therapy;
• long-term use of antibiotics;
• oncological diseases;
• mental illness;
• diseases of the central nervous system;
• increased body temperature;
• anaphylactic shock in history;
• any allergic reaction in the acute phase.

Each of these points can affect the reliability of the results of the analysis.

Preparation for the procedure

Preparation for skin tests implies compliance with certain requirements:

• at least 30 days must have passed since the last manifestation of an allergy;
• two weeks before the analysis you can not take antihistamines ;
• a week you can not use external antihistamines (ointments, creams, gels);
• the body must be in a state of calm - an increase in the level of adrenaline in the blood can affect the effectiveness of the study.

In conclusion, I would like to note that there is no need to be afraid of conducting tests, skin tests are completely painless, and carrying out procedures under constant medical supervision makes them absolutely safe. Any disease is easier to prevent than to treat - in the case of allergies, this statement is more than true!