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.