Allergy skin tests: diagnosing the causes of individual reactivity

Allergies affect millions of people worldwide, and their symptoms can range from mild to life-threatening. To determine what your body is reacting to, skin prick tests are used, a laboratory-clinical method that allows you to quickly identify the allergens responsible for your symptoms. This method is suitable for both adults and children.

When are skin tests needed?

Diagnosis is recommended if the patient:

• seasonal or perennial rhinitis

• itching, rash, hives

• bronchial asthma with an allergic component

• reactions to insect bites

• suspected food or drug allergy

• contact dermatitis after cosmetics or metals

The principle of skin testing

The method is based on provoking a local immune response of the skin. Microdoses of allergens are applied or injected into the selected area (usually the forearm or back). If the body is sensitized to a certain substance, redness, swelling or itching appears at the test site within 15–20 minutes. This is a positive reaction.

Main types of skin tests

Prick test
A drop of allergen is applied to the skin, after which a light puncture is performed through the drop. The method is effective in cases of suspected inhalation or food allergy. Assessment is done after 15–20 minutes.

Scarification test
The allergen is applied to the skin through a micro-scratch. This method is less sensitive, but is used in some cases for household and seasonal allergens.

Application test (patch test)
Allergen patches are applied to the back. The samples are not removed for 48 hours. It is used when contact dermatitis, reactions to cosmetics, metals or chemicals are suspected.

Intradermal test
The allergen is injected into the skin. It is used in more complex clinical cases, in particular to detect drug allergies.

Skin test comparison table

How to prepare for testing

For the results to be accurate, several conditions must be met:

• do not take antihistamines 5–7 days before the test

• do not use creams, ointments or gels on the test site

• avoid physical exertion on the day of the test

• do not take the test if you have a cold, flu, or high fever

• inform the doctor about all medications taken

Contraindication

Skin tests are not performed if:

• child under 3 years old

• the patient is pregnant or breastfeeding

• there is an exacerbation of a chronic disease

• active infection or fever

• existing skin diseases in the sample area

• the patient is receiving immunosuppressive therapy

What does the result look like?

The reaction is detected after 15–20 minutes (in prick tests). The result is evaluated by:

• papule or erythema size

• the presence of itching

• the number of positive responses to various allergens

The assessment is carried out on a scale:

• 0 – no reaction

• • – weak reaction

• ++ – moderate

• +++ – strong reaction

Based on the results, an individual allergen map is created, which is then used to create a treatment program or avoid irritants.

Advantages of skin testing

• fast results

• high accuracy if instructions are followed

• the ability to test dozens of allergens simultaneously

• relatively low cost

• used without complex equipment

Skin tests are an effective method of diagnosing allergies, helping to determine what the body's reaction is related to. Thanks to this method, the doctor receives objective information and can choose the most appropriate treatment or preventive measures.