Sodium metabisulfite--a marker for cosmetic allergy?

A 45-year-old woman developed dermatitis of the face after she applied a cosmetic package comprising day and night creams. Patch tests were performed with the British Contact Dermatitis Society (BCDS) standard, bases + preservatives, and cosmetic series in addition to samples of both creams and the individual constituents. She had positive tests to both cosmetic creams, sodium sulfite from the manufacturer's samples (5% white soft paraffin (WSP)), and sodium metabisulfite (1% pet) in our bases + preservatives battery. Sodium sulfite is a constituent of both cosmetic creams. We assume that the positive test to sodium metabisulfite is a cross-reaction. We hypothesize that a reaction to sodium metabisulfite may be a marker for sulfite allergy in cosmetics and might account for some of the unexplained positives in previous reports.