Relevance of skin tests with drugs in investigating cutaneous adverse drugreactions

Skin tests with drugs can be of value in investigating patients who have de veloped cutaneous adverse drug reactions (CADR), but their specificity and relevance remain to be determined. A false-positive result on skin testing can happen if it is not compared to results in control subjects. When perfo rming intradermal tests (IDT), we have determined the lowest concentrations that induce false-positive results for many drugs, including betalactam an tibiotics, cephalosporins, other antibiotics or non-steroidal anti-inflamma tory drugs. Some drugs in their commercialized form contain sodium lauryl s ulfate and can induce irritation when patch tested as such. When patch test ed with colchicine at 10% in pet. or with a Cytotec((R)) pill (containing m isoprostol) at 30% in pet., respectively, 80% of the 29 and 9 of the 10 neg ative controls developed false-positive results. Lastly, positive results o f patch tests with drugs can be related to contact allergy to one of the co mponents of the commercialized form of the drug, without any relevance to t he investigation of a CADR, as observed in 2 cases with iodine or avocado o il.