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 fails and begins to work against a person, causing such reactions. Scratching tests are one of the methods for identifying a potential allergen.
What is this procedure?
Allergy diagnostics is carried out in patients of different ages. There are two types of sampling:
- the patient is injected with an allergen on the skin, with or without a violation of the skin;
- the sample is injected under the skin.
Based on the results, it is determined how quickly the reaction manifests itself and the degree of severity is revealed. What method to carry it out - the doctor decides. It depends on comorbidities, 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 diagnosisconduct to a person suspected of having a specific allergen.
Indications
Scarification tests for allergies are carried out for suspected diseases such as:
- dermatitis;
- bronchial asthma;
- seasonal runny nose;
- allergic to the sun;
- reaction to food;
- lacrimation;
- itching in eyelids, eyes, nose;
- swelling and inflammation of the skin;
- digestion problems;
- animal reaction, insect bites;
- sensitivity to chemicals and medicines.
Allergy tests are carried out to determine the subsequent methods of treatment, to identify reactions to medicines, cosmetics, animals. Diagnosis is a fairly painless procedure.
Children whose parents are severely allergic to any substance should be prick tested. In the event of allergic reactions in a baby, subject to a hypoallergenic diet and living conditions, diagnostics are carried out to make an accurate diagnosis.
Contraindications
Carrying out scarification tests is possible in the absence of contraindications. The patient must be over 3 years of age. The test should not cause unexpected reactions. Reasons for not testing:
- presence of infectious diseases in the acute phase or exacerbation of chronic ones;
- a person has acquired immunodeficiency syndrome or impaired immunity;
- previously had anaphylactic shock;
- pregnant or breastfeeding;
- asthmatic bronchitis in the acute stage;
- peak allergic reactions;
- mental illnesses.
At the same time, for some groups of patients, it is possible to conduct another effective analysis for the presence of antibodies in the blood. Pregnant women and those with acute illness should not be given any dose of these substances.
Allergens for testing
According to the standard of the European Asthma and Allergy Association, several types can be used for prick tests. They are used in stationary conditions. This method is actively used in the diagnosis of patients in Europe. Allergens most commonly sensitized:
- Pollen. These include birch, cypress, wormwood. If there are olive, ash, nettle, ragweed and plane trees in the patient's region, 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. If the mold Alternaria alternate and Cladosporium album are present in the apartment, respiratory diseases develop.
- Insects. Allergy to cockroaches and cockroach products causes a reaction in some people.
In total there are 40 types of allergens that are carried out during this diagnosis. You can bet no more than 15 at the same time.
How is the procedure done?
Staging locationscratch tests is determined depending on the age of the patient. Adults put a sample in the forearm, children - in the upper back. Children's hands are too small for a lot of tests. If a child needs to approve or exclude up to 5 types of allergens, then a hand can be used.
The procedure is painless. For children, scarification tests are done as follows: letters or figures are drawn on the hand to make the process more interesting for them. For diagnostics, a needle from a syringe or a lancet is used. Small scratches are made at a distance of 4-5 cm. Scratches are minimal, the patient feels discomfort, there is no pain or bleeding.
Before scratching, the surface of the skin is treated with an antiseptic, most often medical alcohol is used. Solutions or extracts of allergens are applied to scratched skin. For the result to be reliable, it is necessary to take a new instrument for each allergen.
Additionally, test samples are applied to the skin, which consist of histamine and glycerin. 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 it is possible to receive a false positive test.
The result is checked after 15 minutes. Based on the change in the skin, a conclusion is made about the presence or absence of the body's reaction to substances.
Evaluation of results
Skin prick tests with allergens are diagnosed within 15 minutes after setting. Resultdetermined on the basis of swelling, redness, itching. A red papule appears. The doctor takes measurements, draws a conclusion and removes the remnants of allergens from scratches.
If the reaction does not appear, then it can be argued that the patient does not have an allergic reaction. Criteria for determining an allergic reaction:
- A questionable result is considered in the presence of redness and the absence of papule. In this case, the patient is additionally examined.
- Papule up to 3 mm - weakly positive result. The allergen has little effect on humans.
- Five millimeters is a positive reaction.
- More than 10 mm - a sharply positive reaction. The same result is given for a reaction that appeared within a few minutes.
- A papule with a diameter of more than 1 cm appeared immediately after the introduction of the allergen. In this case, an antihistamine may be administered.
Treatment is prescribed by the doctor based on the data received.
False results
Scratch test results may not always be accurate. If it is not reliable, then appear:
- false positive result - the test shows the presence of an allergy, but it really is not;
- false negative - the person is suffering from exposure to the allergen, but the test did not show.
Doctors have identified the reasons why the method fails:
- violation of scratches that are too close together;
- violation of storage conditions for allergens, as a resultwhich structural changes and properties of substances have occurred;
- individual reduced skin reaction;
- incorrect preparation for analysis, taking antiallergic drugs.
The most common reason for a false positive result is less than 2 cm between scratches.
False-negative results occur if the patient has not canceled antihistamines three days before diagnosis. In the elderly, 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 believe that they are allergic to a substance, but the test does not confirm this. Most likely, the person is mistaken, and the allergen should be looked for elsewhere. Some plants bloom at the same time, and the pathology occurs on pollen that is not nearby.
Features of the procedure
This type of diagnostics is used to detect more than 40 allergens. A scratch test for antibiotics, pollen, mites, animals and insects is possible after three years. In this case, the child must be he althy. Therefore, at an earlier age, a blood test is performed.
Skin tests take longer than blood tests and are limited in terms of allergens. More than 200 types of irritants can be donated.
Scarification tests cause side reactions in the form of blisters and redness. SuchReactions are rare, but they do happen. The most severe 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 at the site of the allergy test, the introduction of additional drugs and ointments is required.
Another feature of skin tests is the impossibility of conducting them at the time of the onset of an allergic reaction.
Preparations
Proper preparation for this serious procedure will help avoid false negative results. The doctor prescribes a standard set of tests to the patient - blood and urine.
Be sure to stop taking antihistamines within 72 hours. If during this period the allergy has increased again, then the sampling will have to be postponed. Do not use within 10 days prior to analysis of sedatives and antidepressants.
