Sulfite contact allergy

In the last 2 years, 2,894 consecutive eczematous patients were patch tested with sodium metabisulfite 1% pet. Positive reactions were elicited in 50 subjects (1.7%). All 50 patients were also positive to potassium metabisulfite 1% pet. and sodium bisulfite 1% and 5% pet., while only 2 of them were positive to sodium sulfite 1% pet. Prick tests and intradermal tests with a sodium metabisulfite solution (10 mg/ml) were negative. No flare-ups of dermatitis or patch test were provoked by oral challenge with 30 mg and 50 mg of sodium metabisulfite. The dermatitis was taken to be occupational in 7 cases. In only 5 out of 43 non-occupational cases was the positive reaction considered relevant.