Allergies occur when the immune system overreacts to the substances from the external environment that are usually harmless. They can develop at any age and tendency toward allergies is often hereditary.
Substances that cause allergies are called allergens, they are harmless, but in some individuals they cause allergic reactions. There are substances that provoke allergic reactions more often than the others.
Allergens can be inhalatory (that are inhaled), nutritional (from food), as well as contact (those that produce reaction when in contact with the skin).
Symptoms can occur in the form of systemic (general) and localised allergies when manifested on the skin or mucous membranes that they come into contact with and through which they enter the body.
Skin lesions can occur as eczema reactions at the place of contact with the allergen, in a form of redness, itching and dryness or in the form of hives (urticaria) characterised by redness, itching and blisters.
Inhalatory allergens can cause allergic rhinitis characterised by itching, sneezing, increased nasal secretion. One can also develop allergic bronchial asthma with dry cough and feeling of suffocation, but also allergic conjunctivitis, characterised by itching, redness and eye lacrimation.
Among systemic allergies, the most common are food and drugs, characterised by urticaria or hives on the skin, as well as suffocation, to the most severe allergic reaction in the form of anaphylactic shock.
Various tests can be used to find out what kind of substance is causing an allergic reaction. Skin prick and epicutanetesting are considered reliable in making a diagnosis, and safe and quick to perform.
This test is used in early allergic reactions mediated by IgE antibodies.
These reactions can manifest themselves in the form of allergic rhinitis and conjunctivitis, bronchial asthma and hives (urticaria).
This test is more important in respiratory atopy and less in dermatology.
How is prick testing performed?
This type of testing is carried out on inhalatory and nutritional allergens. In our clinic, we perform testing for inhalatory allergens, those that can be found in the air and by inhaling them they come into contact with the mucous membrane and cause an allergic reaction. We use a palette of standard inhaled substances which most often provoke allergic reactions.
It consists of the twelve most common allergens among which house dust, mites, grass pollen, grass root, animal hair and others, and solutions of histamine and saline are used as a control.
Patients must be without antihistamine therapy for at least 48 hours before therapy. It is performed by applying a drop of allergen solution and control substances to the inner side of the forearm, to the marked spot. Then, the surface layer of the skin is pierced with a lancet device and a small amount of allergen is introduced.
After 20 minutes, the presence and the diameter of urticaria is detected. A severe reaction may happen during testing with intense redness, blisters, intense itching spreading beyond the marked places, when adequate therapy can be prescribed.
Epicutaneous testing (or patch testing) is used to detect triggers for eczema lesions on the skin that develop after repeated contact with certain substances, characterised by redness, itching, blisters and skin flaking.
That’s how we make a diagnosis of contact allergic dermatitis, as well as distinguish irritant from allergic dermatitis.
A standard, professional and target allergen battery can be used.
How is epicutaneous testing performed?
Testing is carried out by placing the allergen in an appropriate concentration that does not irritate but is capable of causing an immune reaction, on clean (healthy) skin of the using a filter paper and covering it with a specially prepared patch.
Nowadays, specially prepared chambers are also used.
The patch is removed after 48 hours, and the readings are performed 48h, 72h and 96h the application of the testing substance.
During the patch-wearing period (48h), it is important that this area does not get wet and that the patch is not taken off.
In our practice, we use a standard allergen battery with 18 substances.
When necessary, other substances (professional and target) are used which are considered suspicious by anamnestic data. The most common allergens in our population are potassium chromate, cobalt chloride, nickel sulfate, latex, paraphenylenediamine, etc.
If a person is allergic to one of the substances, at the place of contact redness, itching and sometimes blisters appear.
Depending on the intensity of the reaction, the test results are marked from negative (-) to extreme positive reaction (++++).
When epicutaneous testing detects a substance that triggers an allergic reaction, preventing further exposure to this allergen allows faster withdrawal of symptoms and healing of skin lesions.
With proper anamnestic data and clinical picture, rapid and effective detection of allergens with the help of allergy testing allows dermatologist to make a diagnosis and helps the treatment of the appropriate allergy type.