How does the skin test reaction look like?
How does the skin test reaction look like?
The applied allergens are bound on the antibodies molecules IgE - on the outside part of the mastocytes and through the transfer of the signal their degranulation and the allergic reaction mediators release occur. These initiate the reaction through the affect on the surrounding blood vessels, the symptoms of which are the flush, the itch and the swelling with the diameter of several millimetres in the place of the injection. On the reaction, which starts approximately after 5 minutes from the allergen application, takes part also the so called substance P, which is released from the sensitive nerve ending, after the histamine stimulation. The reaction culminates in the period of 15-20 minutes, when the doctor subtracts it, after this time the reaction decreases.
The skin test realisation is not painful for the patient. On the palm side of the forearm the drops of the examining allergens are applied. In every drop a gentle puncture with the plastic or metal tool with the small sharp top is made. The skin is punctured only on the top skin layer so that the place does not have to bleed at all. After 20 minutes the reaction is judged. Places, which are either red or swollen in the same way as after applying the histamine, indicate that the reaction is positive. The patient can react to one or ore allergens. Beside the reaction when the small papule with the diameter of several millimetres appear, which is the most common reaction, the more extensive local reaction – of several centimetres, in rare cases even the swelling of the hand come about. These reactions cease to occur spontaneously after several hours.
In addition to the immediate reaction the patient can react in the so called later phase, when the papules appear after several hours. The patient deducts and informs the doctor of the reaction by himself/herself. The skin tests represent the allergist diagnosis basis. Together with the detailed taken anamnesis they are sufficient for the majority of the patients sensitive to common inhalation allergens for the typical symptoms of the diagnosis. Their role in the diagnosis is hence important, which relates to the fact that their preparation and realisation should be paid attention to.
The skin tests can be characterised as indirect provoking tests. They are called indirect, since their positives and negatives prove the sensitization of the human body. The presence of the specific IgE antibodies to applied allergen is proved on the skin without giving the information on the reactivity of the particular target organ (unless the target organ is the skin itself). Standard prick tests are used. They are made by the pharmaceutical companies, which prepare them according to the strict formulas. The content of all solutions with the allergens is diluted exactly together with the known analysed components of the particular chemical. The food allergens to the prick tests are chosen similar according to the patients. In the basic scale the eggs, nuts, milk and hesperidium should not be omitted. As far as the patient has not only a food allergy, but also the inhalational allergy, we add the cross reacting foodstuffs (birch-apple, Artemisia-celery, mites-crabs, latex-banana, etc.).
The professional airways allergic illnesses have increasing tendency. The allergens are represented by the whole range of various factors of both, the vegetable and animal origin, but also by the chemical agents. Besides the pharmacotherapy, which does not differ from the common recommended procedures, the fundamental step is the immediate transfer of the patient from the exposition of the cause, which is necessary to be defined. To the testing process the chemicals, which are not tested with the traditional patients, are added, as well.
The contact allergy diagnosis skin tests are made by putting the analysed chemical on the skin. More information is provided in the chapter about the contact allergy.
Tags: allergens, contact allergy, Skin, skin tests