Allergy Diagnostics and Allergy Testing
In the case of the diagnosis of allergic diseases, there is the special problem that the disease symptoms - such as runny nose, asthma or eczema - are overwhelmed by an enormous amount of allergy-causing substances. In order to find out from the at least 20,000 hitherto scientifically known allergens, which is appropriate for the patient, it is necessary to use complex diagnostic methods. Allergy diagnostics generally take place in four stages.
1. Allergy diagnostics: Anamnesis
From the survey of the history of allergic diseases (anamnesis) already valuable information about the possible allergy trigger can be obtained. In addition, the domestic and occupational environment, living and nutritional habits as well as the at least orientated recording of the psycho-social environment are to be taken into account.
In particular, self-observed relationships between the allergic symptoms and possible allergens as well as the environmental conditions of a private and professional nature are to be recorded. Particularly important are the detection of the onset of disease (also possible "precautions") and the references to the primary allergen contact.
2. Skin Tests
Skin tests (Prick test, Intracutaneous test, Scratch test and rubbing test) are a foundation of allergy diagnostics. Here, samples of various substances (possible allergens) are applied to the skin and observed whether an allergic reaction occurs at this site (as a pustule or wheeze). Depending on the diagnostic objective, the physician may restrict himself and examine the suspected allergens by means of individual tests ("confirmation test"). In most cases, however, this is a search diagnosis, in which it is important to record as wide a range of allergens as possible by group extracts in a single session.
Skin tests lead to false results when antihistamines or corticosteroids are taken at the same time. Therefore, antihistamines should be avoided five days before an intended skin test. For infants , these tests are not ideal.
Prick test: Apply a drop of the test solution on the arm and then pierce the skin with the Prick lancet at about 1 millimeter deep. In the case of an existing allergy to the test substance, a whey has formed at this point after approximately 20 minutes. For allergies of the immediate type, the prick test is applied as a standard method. You can also Diagnosis the Diabetes.
Intracutaneous Test : In this case the allergen is injected with a needle into the skin. The intracutaneous test is about 10,000 times more sensitive than the Prick test, but more often results in false positive results, especially in food allergens.
Scratch Test : The skin is superficially scratched through the applied test solution. Because of the relatively large skin irritation, this test is not always clear. Therefore, the scratch test has become less important today.
Rubbing Test : The allergen is repeatedly rubbed back and forth on the inside of the forearm. This test is used when there is a high degree of sensitization of the patient. Since this test is carried out with the natural allergen, it is also suitable if the allergy-releasing substance is not available in an industrially prefabricated version.
Epicutant test (patch test): Patches with allergenic substance are glued to the skin (preferably back) and read after 24, 48 or 72 hours. This test is used to identify type IV allergens. Most of the Causes of Allergies.
3. Lab Tests
In the case of blood tests, the ability to react and specific sensitization to the investigated allergens in the laboratory are examined with the aid of blood samples. One criterion is the presence of specific IgE antibodies. The proportion of antibodies (immunoglobulin E) in the blood is measured using modern methods. Immunoglobulin E is formed as a reaction to the body-borne substances, to which the immune system of an allergic reaction is sensitive.
Blood tests are therefore recommended for allergy diagnosis, especially for babies and small children, as they are less stressful for the small patients, as only blood collection is required. Above all, however, there is no danger for the child, even if the child is overly sensitive. In addition, the use of drugs does not influence the result, while skin tests can be distorted as a result. Finally, the doctor can even predict the likely allergy career of his patient based on the results of the laboratory test and often prevent worse with appropriate counter-measures.
4. Provocation Test
The interpretation of the test results always requires a check by collecting a "follow-up" (Is the patient exposed to the allergen at all? Whether the IgE antibody determined by positive skin tests and / or blood tests corresponds to a current clinical efficacy of the respective allergen can only be finally clarified by direct testing at the respective organ using a provocation test.
Provocation Test : In the provocation test, the clinical symptom (for example conjunctivitis with redness and eye tears, asthma, rash, eczema) is reproduced by extensive imitation of the "natural" allergens.
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