Gentowa

The skin tests are necessary supplements of all basic allergist examinations. The allergic hypersensitiveness proof was discovered by Charlie Blackley already in 1865. The technique

was later on improved by Grant Lewis, Pepyes and others, who introduced the prick test (stinger) usage. Nowadays the standardized method introduced by the European allergist and clinical immunology academy.

The skin test in based on the fact, that sensitive allergic patient has specific antibodies against the allergens not only in the particular organ, in which the clinical symptoms are active, but also in the cell membrane – mastocyte which are in the skin. While testing, the suspect allergen is injected into the patients´ skin near the forearm. The allergen choice is made according to the patients´ data on the clinical symptoms period. The standard group of allergens, which includes the following, is used:

● trees pollen

● grass pollen

● rye

● worm wood

● ambrosia

● mould

● feather

● mites

● positive control (histamine)

● negative control (usually a solution with dissolved allergens)

According to the seasonality, others allergens are added. If the patient is in the contact with the animals, the animal allergens (dog, cat, etc) are tested, as well. Before the testing the patient should cease the anti allergic treatment (the antihistamines for at least one week), but others, as well. For example many preparations used by the psychiatrists relieve even the skin reaction at the skin tests.

When possible, the patient should be tested even off pollen season. It is not appropriate to test somebody during or right after the infection since it can cover the reaction, as well. For checking the skin test realisation correctness beside the allergens, the positive and the negative control is injected. As the positive control histamine is used – a chemical, which is released during the allergic reaction in general, i.e. test with this chemical can be positive even in the case of the health people. If this reaction after the testing is negative, the test is not valid, since some of the processes or the medications relieved all reactions.

The negative checking is, on the contrary, is injected in order to exclude the reaction, which is only mechanical – the injury or the injection itself, or the allergic reaction to the solution, eventually to the conservative chemical in the allergen solution. The skin tests allergens are made commercially. Their content and dilution are standardised.

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.