[Value of the patient's own test substances in epicutaneous testing]

Patch testing with commercially available test kits of known allergens often leads to detection of the responsible allergen. In many cases, however, the responsible allergen cannot be found unless the patient's "own" products or chemicals are tested. An analysis of 2460 patch tests with patch test kits proposed by the DKG (German Contact Allergy Group) and a positive history of a patient's own substance showed positive results in 208 patients with 289 products. In 44% (129 out of 289) the responsible allergen could only be found by testing the patient's own substances, in 56% (160 out of 289) the same allergen as was responsible for the positive result with patients' endogenous substances was positive in one of the commercially available test kits. The substances that tested positive were medical products/adhesives (45%), cosmetics (39.4%), rubber materials (4.1%), leather materials (0.7%) and others (10%). Subsequent testing of the different components of the patients' own substances that tested positive was carried out in 45 cases and resulted in the detection of new allergens, such as tris-(2-hydroxyethyl)isocyanurate triacrylate. In 27 patients the endogenous substances had tested positive in the course of testing for occupational dermatitis, and in 10 of these positive testing of a patient's own product resulted in notification of an occupational dermatitis. These results show, that patch testing with the patients own products if very important for the finding of the responsible or even new allergens.