The aim of the present study was to evaluate the influence of individual explanatory factors, such as sex, age, atopy, test time and presence of diseased skin, on clinical patch test results, by application of multivariate statistical analysis. The study population was 2166 consecutive patients patch tested with the standard series of the International Contact Dermatitis Research Group (ICDRG) by members of the Danish Contact Dermatitis Group (DCDG) over a period of 6 months. For the 8 test allergens most often found positive (nickel, fragrance-mix, cobalt, chromate, balsam of Peru, carba-mix, colophony, and formaldehyde), one or more individual factors were of significance for the risk of being sensitized, except for chromate and formaldehyde. It is concluded that patch test results can be compared only after stratification of the material or by multivariate analysis.

In a 3-year period, 551 patients were patch tested with chlorhexidine gluconate 1% in water. 14 patients showed a strong and obviously relevant reaction. A severe dermatitis developed during treatment with a chlorhexidine preparation in 10 patients with venous or traumatic ulcers of the leg, and in 4 patients with skin infection on the face and/or scalp. So far the sensitizing potential of chlorhexidine has probably been underestimated.

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Patch tests with metallic tin in 73 nickel-sensitive patients revealed 6 positive allergic reactions. Only 4 doubtful reactions were seen, which makes irritancy unlikely. The relevance and clinical significance of the unexpected finding deserves further evaluation.

In two patients urticaria was elicited by contact with nickel-containing objects. Chamber-prick test with nickel sulfate 2.5% in pet. evoked a strong urticarial reaction in both patients. In one of the patients contact with plastic articles also provoked urticaria. A 20-min patch test with several articles of plastic (polyethylene and PVC) and with butylhydroxytoluene (BHT) 1% in ethanol elicited urticarial reactions. BHT is used as an antioxidant in plastic. Furthermore, open patch test with oleylamide (amide of oleic acid) 0.1% in ethanol elicited a strong urticarial reaction in 20 min. This chemical is used as a slipping agent in plastic.