Frequency | Hay fever

Frequency

Between 15% and 25% of the population in western, “civilized” countries are affected. The disease is even more widespread among young people, at over 30%. Due to a changed lifestyle, hay fever and allergic diseases are increasing strongly.

Diagnosis

Basically, the detection of hay fever, as with any allergy, follows a scheme of up to four steps: The medical history (anamnesis) of the patient describing the above-mentioned symptoms is the first step in the detection of a pollen allergy. This is followed by a physical examination, which includes in particular an examination of the nasopharynx and eyes. An existing allergy can also be proven by various tests: The principle of the prick test is to apply a small amount of the suspected allergen in the form of a standardized solution prepared in the laboratory to a puncture mark caused by a fine lancet on the inside of the forearm and to assess the skin reaction after a quarter of an hour.

The test is then considered “positive” in the sense of an existing allergy (not as an evaluation!) if a relevant redness and swelling (wheal) occurs. The prick test is the test that is routinely used today and by far the most frequently used test; alternatives such as the scratch test (use of the unmodified allergen, no standardized extract solution) or the significantly less reliable rub test (the unmodified allergen is rubbed over the intact skin of the inner side of the forearm) are only rarely used.

The prick test is both an unspecific screening test for suspected diseases and a confirmatory test for allergies to one or more specific substances. For all skin tests, however, it applies that a sensitivity (medical: sensitization) detected in this way has no disease value in itself; only the existence of symptoms in the case of a positive test result allows the diagnosis of an allergy. If a skin test is inconclusive or not feasible (e.g.B.

in infants) a blood test can provide further clarity: The principle here is to detect the proteins produced by the immune system that are specifically directed against the triggering allergen (and are then called specific IgE antibodies). Numerous different methods are available for this purpose. The best known is the RAST (abbreviation for Radio Allergo Sorbent Test).

Existing IgE antibodies are detected by means of other proteins that are structurally similar to the allergen and labelled with a radioactive substance. (The chemical similarity is usually limited to certain sections, so-called epitopes, and is the cause for the specific binding of the sought IgE antibodies). In detail, this proceeds as follows: The doctor takes blood from the patient.

The serum, purified from solid components, is applied to an industrially prefabricated disc coated with the allergen to be detected (medical: incubated, i.e. under the required environmental conditions such as sufficient heat, low humidity, etc.). Any antibodies present in the patient’s blood can now react with the antigens (in this case the allergens) applied to the disc and form complexes, i.e. stable chemical compounds. These complexes are then detected by reaction with the radioactively labelled proteins by measuring the radioactivity of the entire sample. (This is done by removing the radioactive proteins that have not reacted with any of the complexes of allergen and patient antibody to be detected).