Allergy Tests: What They Are, Types, and How to Interpret Results

Allergy tests are examinations that show which substances the body reacts to as allergens. They are prescribed when allergy is suspected to link symptoms to a specific trigger.

What allergy tests are and why they are done

Allergy is the body's reaction to something usually harmless: pollen, dust, animal dander, foods, insect stings, certain medications. Substances that cause such a reaction are called allergens. Allergy tests are performed to determine individual tolerance to specific substances and to understand what exactly causes symptoms. Testing is also used when it is necessary to assess the tolerability of a drug that has not been used in the patient before.

Types of allergy tests: skin tests and blood tests

Skin tests come in several types. In a prick test, a drop of allergen is applied to the skin, usually on the forearm or back, and a prick is made so the substance enters under the skin surface; the result is visible after 15–20 minutes, and several allergens can be tested at once. An intradermal test is injected into the skin, usually on the upper arm, and is used to test for bee venom or penicillin, and also when the prick test is negative but the doctor still suspects allergy; it is not done for food allergens. A patch test is used for skin reactions after contact with a substance: allergens are fixed on the skin for 48 hours, and the area is examined after 72–96 hours.

A blood test for allergens allows a comprehensive assessment of sensitivity, but the result takes longer. Provocation tests are used rarely—when other methods have not identified sensitivity.

How to take or undergo allergy tests: what is known about preparation

Before testing, the doctor asks about past illnesses, place of work and residence, lifestyle, and eating habits. Medications containing antihistamines—both prescription and over-the-counter—can alter skin test results. The doctor will say which drugs and when to stop; if this cannot be done due to severe symptoms, this is reported in advance so that another approach to examination can be chosen. Medications without antihistamine action, such as asthma inhalers, montelukast, and nasal steroids, do not need to be stopped.

• Skin tests may cause mild discomfort at the injection site.
• A positive reaction looks like redness, itching, and swelling, similar to an insect bite.
• Patch tests sometimes cause irritation or itching that resolves after removal.
• Serious reactions during skin tests are extremely rare, but the doctor is prepared for them.

What class 2 weakly positive means and how to read the result

A negative result means no skin changes in response to the allergen; most often this indicates no allergy, although in rare cases the test may be negative despite a reaction. A positive result is redness and swelling, the so-called wheal; the stronger the response, the higher the likely sensitivity to the substance. However, a person may have a positive reaction to a substance and have no problems with normal contact with it; such false-positive results are especially common when testing food allergens. Therefore, the class value indicated on the report is not a diagnosis in itself: the doctor correlates the numbers with symptoms and only then suggests lifestyle changes.

Allergy in a child's blood: how results are assessed in children

In children, as in adults, skin tests and blood tests are used, and the decision on a specific examination is made by the doctor. It is useful for parents to understand that a positive test result does not yet mean clinical allergy: false-positive responses are possible, especially when testing food allergens. Assessment is based on the combination of symptoms, their connection with contact, and examination results, not on a single number from the report.

When the result may be inaccurate and when a doctor's consultation is needed

Skin tests are usually accurate, but false-positive and false-negative responses are possible. If you or your child suspect an allergy, the doctor may prescribe an examination or refer you to a specialized clinic.

The examination itself is not a reason to call an ambulance; 103 or 112—if lips, mouth, throat, or tongue suddenly swell, breathing becomes rapid or difficult, there is a feeling of tightness in the throat or difficulty swallowing, the skin, tongue, or lips turn blue, gray, or pale, the person suddenly becomes confused, drowsy, or loses consciousness, and the child becomes lethargic and does not react as usual.

This material is for reference: it explains the essence of the examination but does not replace consultation with a doctor who assesses symptoms and results together.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer