The authors report a study of allergic contact dermatitis in 329 Portuguese children of 14 years or younger. 170 children (64 male and 106 female) reacted to 1 or more allergens. Most of these were in the 11-14 years group. The main allergens were nickel, thimerosal, cobalt, mercury, fragrance-mix and potassium dichromate. Nickel reactivity predominated in females over the whole group, but a greater number of males younger than 5 years reacted to nickel. The number of positive reactions increased with age, but this was not accompained by an increase in the % of relevant tests. 12 children, all of them 13 or 14 years-old, had an occupational allergic contact dermatitis.

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There has been increasing interest in characterizing the sensitizing moiety of thimerosal [TIM], following the finding that patients with photosensitivity to piroxicam are allergic to the thiosalicylic acid [TIO] moiety of TIM. For this purpose, the authors have conducted 2 studies in TIM-sensitive patients. In the 1st, of 175 patients tested with TIO and ammoniated mercuric chloride [HGAM], 45.7% reacted only to TIM, whereas 45.7% reacted also to TIO and 17.7% also to HGAM; 9.1% reacted to both TIO and HGAM. In the 2nd, of 47 patients tested with TIO and ethylmercuric chloride [ETHG], 87.2% reacted to ETHG, 44.7% to TIO and 31.9% reacted to both. None of the patients reacted only to TIM. The authors conclude that thimerosal allergy is due either to the mercuric moiety or to thiosalicylic acid, with no cases of sensitivity only to the whole molecule of TIM. TIM-sensitive patients are mainly allergic to the mercuric moiety, but among them there are a large number of TIO-sensitive patients, and these should be advised to avoid piroxicam.

During the last 3 years, 9 patients with a photosensitive eruption related to piroxicam therapy were seen. In all but one, it occurred within 4 days of first exposure to the drug. 7 patients required systemic corticosteroids, and 2 hospitalization. Clinical, histological and provocation studies were not conclusive in classifying the eruption as photoallergic or phototoxic. Experimental studies including photohaemolysis, Bacillus subtilis culture and nuclear magnetic resonance showed: (i) in irradiated piroxicam solutions, there was more haemolysis; (ii) in irradiated Petri dishes, piroxicam solutions showed greater inhibition of growth of B. subtilis; (iii) Piroxicam's NMR spectrum is not modified after irradiation. The results provide evidence of piroxicam phototoxic potential.