Allergy is the most unexplored disease. Doctors have learned to identify allergens and make life easier for patients. At the same time, it is not completely known why the immune system malfunctions and begins to work against a person, causing such reactions. Scarification tests are one of the methods for identifying a potential allergen.
What is this procedure?
Allergodiagnosis is carried out in patients of various ages. There are two types of sampling:
- the patient is injected with an allergen to the skin, with or without a violation of the skin;
- the sample is injected under the skin.
The results determine how quickly the reaction manifests and reveals the severity. What method to carry it out - the doctor decides. It depends on concomitant diseases, the suspected allergen and age group.
Scarification skin tests are the most informative method for determining individual intolerance. The patient experiences a minimum of negative emotions. Doctors recommend this type of diagnosis to a person with a suspicion of a specific allergen.
Indications
Allergy screening tests are performed for suspected diseases such as:
- dermatitis;
- bronchial asthma;
- seasonal runny nose;
- allergy to the sun;
- reaction to food;
- lacrimation
- itching in the eyelids, eyes, nose;
- swelling and inflammation of the skin;
- digestion problems;
- reaction to animals, insect bites;
- sensitivity to chemical and medical preparations.
Allergy tests are carried out to determine subsequent treatment methods, to identify reactions to medicines, cosmetics, animals. Diagnosis is a fairly painless procedure.
For children whose parents are severely allergic to any substance, it is advisable to carry out scarification tests. In the event of allergic reactions in the baby, subject to a hypoallergenic diet and living conditions, diagnosis is carried out to make an accurate diagnosis.
Contraindications
Scarification tests are possible in the absence of contraindications. Patient must be over 3 years old. The test should not cause unexpected reactions. Reasons why you can not diagnose:
- the presence of infectious diseases in the acute phase or exacerbation of chronic;
- a person has acquired immunodeficiency syndrome or impaired immunity;
- previously had anaphylactic shock;
- pregnancy or breastfeeding;
- asthmatic bronchitis in the acute stage;
- peak allergic reactions;
- mental illness.
At the same time, for some groups of patients, another effective analysis for the presence of antibodies in the blood is possible. Pregnant women and people with an acute course of the disease should not be given any dose of these substances.
Allergens for testing
According to the standard of the European Association for Asthma and Allergy, several types can be used for scarification samples. They are used in stationary conditions. This method is actively used in the diagnosis of patients in Europe. Allergens that most often cause the body's sensitivity:
- Pollen. These include birch, cypress, wormwood. If there are olive, ash, nettle, ragweed and plane tree in the patient's region of residence, sensitivity tests should be done.
- Ticks live in apartments. Most often found in soft toys, carpets, sofas.
- Animals. The main source of allergens are cats and dogs.
- Mold. In the presence of Alternaria alternate and Cladosporium album molds in the apartment, respiratory diseases develop.
- Insects. Allergies to cockroaches and their waste products cause a reaction in some people.
In total, there are 40 types of allergens that are carried out during this diagnosis. At the same time, you can put no more than 15.
How is the procedure performed?
Placement of scarification samples is determined depending on the age of the patient. Adults put a test in the forearm, children - in the upper back. Children's hands are too small for a large number of tests. If a child needs to approve or eliminate up to 5 types of allergens, they can use a hand.
The procedure is painless. Scarification tests are done for children as follows: letters or figures are drawn on the hand so that the process goes more interesting for them. For diagnostics use a needle from a syringe or a lancet. At a distance of 4-5 cm make small scratches. Minimal scratches are made, the patient feels discomfort, there is no pain and bleeding.
Before scratching the surface of the skin is treated with an antiseptic, most often use medical alcohol. Allergen solutions or extracts are applied to scratched skin. In order for the result to be reliable, it is necessary to take a new tool for each allergen.
Additionally, test samples, which consist of histamine and glycerin, are applied to the skin. Most people respond to histamine. If there is no reaction to this drug, then the result will most likely be false. There should be no reaction to glycerin. If it appeared, then a false-positive test is possible.
The result is checked after 15 minutes. Based on changes in the skin, a conclusion is made about the presence or absence of an organism's reaction to substances.
Evaluation of the results
Skin scarification tests with allergens are diagnosed within 15 minutes after setting. The result is determined on the basis of swelling, redness, itching. A red papule appears. The doctor takes measurements, draws a conclusion and removes the remaining allergens from scratches.
If the reaction did not appear, then it can be argued that the patient does not have an allergic reaction. The criteria by which an allergic reaction is determined:
- The doubtful result is considered in the presence of redness and the absence of papules. In this case, an additional examination of the patient is carried out.
- Papule up to 3 mm is a weakly positive result. Allergen has a negligible effect on humans.
- Five millimeters is a positive reaction.
- More than 10 mm is a sharply positive reaction. The same result is set in the reaction, which appeared within a few minutes.
- Papule with a diameter of more than 1 cm appeared immediately after the introduction of the allergen. In this case, the introduction of an antihistamine is possible.
Treatment is prescribed by a doctor based on the data received.
False results
Scarification test results may not always be accurate. If it is not reliable, then appear:
- false positive result - the test shows the presence of allergy, but it actually is not;
- false negative - the person suffers from exposure to an allergen, but the test did not show.
Doctors have identified the reasons why the method fails:
- violation of the statement of scratches that are too close to each other;
- violation of the storage conditions of allergens, resulting in structural changes and properties of substances;
- individual reduced skin reaction;
- improper preparation for analysis, taking anti-allergic drugs.
The most common reason for a false positive result is that the distance between the scratches is less than 2 cm.
False negative results appear if the patient has not canceled antihistamines three days before the diagnosis. In elderly people, skin sensitivity is reduced, which leads to false results. The same reaction can be observed in babies. For this reason, they do not carry out scarification tests.
Sometimes patients are sure that they are allergic to any substance, and the test does not confirm this. Most likely, the person is mistaken, and you should look for an allergen in another place. Some plants bloom at the same time, and pathology occurs on pollen, which is not nearby.
Features of the procedure
This type of diagnosis is used to identify more than 40 allergens. Scarification test for antibiotics, pollen, ticks, animals and insects is possible after three years. In this case, the child must be healthy. Therefore, at an earlier age, a blood test is performed.
Skin tests take more time than a blood test, and are limited in the number of allergens. Blood can be donated to more than 200 types of irritating substances.
Scarification tests cause adverse reactions in the form of blisters and redness. Such reactions occur rarely, but still happen. The strongest that can develop is anaphylactic shock. In this case, the introduction of antihistamines is urgently required.
Skin reactions after the test usually go away within a few hours. With a prolonged allergic reaction, additional drugs and ointments are required at the site of the allergy test.
Another feature of skin tests is the inability to conduct them at the time of the onset of an allergic reaction.
Preparatory Activities
Proper preparation for this serious procedure will avoid false negative results. The doctor prescribes the patient a standard set of tests - blood and urine.
Be sure to stop taking antihistamines in 72 hours. If during this period the allergy intensified again, then the production of samples will have to be postponed. It is unacceptable to use for 10 days before the analysis of sedatives and antidepressants.