Allergic contact dermatitis caused by sodium metabisulfite: a challenging allergen. A case series and literature review

Background. Sulfites, preservatives and antioxidants used in the cosmetic, pharmaceutical and food industry are contact allergens whose relevance seems to be difficult to establish. Objectives. To perform a retrospective study on patients patch tested with a sulfite. Materials and methods. Between 1990 and 2010, 2763 patients were patch tested with sodium metabisulfite. The reactions were considered to be relevant if there was a clear relationship between the dermatitis and sulfite exposure. Results. One hundred and twenty-four (4.5%) of 2763 patients patch tested positively to sodium metabisulfite. The most frequent localizations of the lesions were the face (40.3%) and the hands (24.2%). Six patients also reported systemic symptoms. Thirteen cases (10.5%) were occupational, 10 of them presenting with hand eczema. Sodium metabisulfite was the single allergen found in 76 cases (61.3%). The reactions were considered to be relevant in 80 cases (64.5%), of which 11 were occupational. Conclusions. Allergic contact dermatitis caused by sulfites is frequent and often relevant. One should be aware of possible relevant sources of exposure, particularly in occupational settings such as hairdressing and the food industry, and in pharmaceutical and cosmetic products. Patch testing with sodium metabisulfite, which seems to be the best indicator for sulfite contact allergy, is also useful in cases of immediate reactions to sulfite-containing products.