Hauttestungen bei Medikamentenallergien

Abstract

Only approximately 15% of all adverse drug reactions are caused by true drug allergies. It can be difficult to make the diagnosis of a drug allergy and to identify the causal drug. The clinical pattern, including the temporal relationship, usually enables a suspected diagnosis only. In most situations skin tests are the allergological investigations of first choice. In prick tests and other intradermal tests a small amount of the incriminated drug is administered into the upper dermis, where it comes into contact with peri-vascular mast cells and T-lymphocytes. If the patient is sensitized, such contact may induce a local allergic skin reaction of both immediate and delayed type. In the patch test the incriminated drug is applied to the skin by an occlusive plaster. It can then permeate the epidermis and induce local skin reactions, predominantly of the delayed type. The sensitivity of skin tests is limited. It decreases in immediate type reactions, if the reaction dates back more than 6 months. Additionally it depends on which drug is involved. For the investigation of IgE-mediated allergies against the penicillin core-structure a test kit is a commercially available. However, the investigation of allergies against betalactam-antibiotics requires the inclusion of the offending drug, so that immunoreactions against the side chain structures can be identified. IgE-mediated allergic reactions against local aesthetics are extremely rare. The diagnostic value of intradermal skin tests in immediate reac-tions is limited because of a rather low specificity. T-cell mediated contact sensitizations against topically administered local aesthetics occur more frequently (often with ointments for haemorrhoids). According to recent data both immediate and delayed type reactions against radio-contrast media can be immune mediated and be reliably diagnosed by skin testing. IgE mediated allergies against heparins are rare. However, T cell mediated reactions against sub-cutaneously administered preparations are more frequent. The sensitivity and specifity of skin testing in the evaluation of such allergies are not known.