Contact allergy and intolerance to sulphite compounds: clinical and occupational relevance

Abstract

Sulphites are widely used as preservatives and antioxidants, e. g., in the food, cosmetic, and pharmaceutical industries. They are known to trigger epidermal sensitizations and associated eczematous contact allergic skin reactions; to identify these, patch testing is performed using sodium disulphite (= sodium metabisulphite; CAS 7681-57-4). In addition to this, inhalation or oral exposure to sulphite can cause the clinical picture of sulphite intolerance, including bronchoconstriction, urticaria, cardiovascular, intestinal, and/or life-threatening anaphylactic reactions, the identification of which requires challenge testing. This review discusses the prevalence of sulphites, their chemical characteristics, statutory regulations and limit values; sulphite-related diseases and their diagnosis; the occupational significance of sulphites as contact allergens in the literature published between 1968 and 2015; and the current incidence of contact sensitizations in the patient collective at a dermatology practice. Individual cases of inhalative occupational sulphite intolerance were also analyzed. A reaction incidence of 3.1% (++ or +++ reaction on day 4) to sodium metabisulphite (1% in Vaseline) was determined in a 10-year collective comprising 780 patients tested at a dermatology practice; in none of these cases was occupational relevance identified. In contrast, the rate of positive test reactions to sulphite was 1.1–4.5% in eight large patch test collectives. Although occupational relevance in the positive test results (depending on selection criteria) was between 0 and 100%, it was predominantly (in six of eight studies) between 5 and 14%. Approximately 50 cases involving occupational allergic contact dermatitis due to sulphite have been published in the literature over the last 45 years, as well as a small number of cases of occupational sulphite intolerance. In summary, epidermal sensitizations to sulphite are rarely of occupational relevance. Despite the wide prevalence of sulphites in the form of preservatives and antioxidants, the low number of cases documented in an occupational dermatological context suggests that occupational sulphite exposure only rarely exists in disease-triggering form.