Risk of sensitization to preservatives estimated on the basis of patch test data and exposure, according to a sample of 3541 leave-on products

Background. The risk of sensitization cannot be derived from the frequency of sensitization to allergens alone, but exposure should be considered. Objective. To estimate the risk of sensitization to selected preservatives. Methods. The occurrence of preservatives in 3541 leave-on products based on the labelling of the ingredients was documented. Frequency of sensitization to preservatives was analysed on the basis of Information Network of Departments of Dermatology data for 2006-2009. As an estimate of sensitization risk, the sensitization exposure quotient (SEQ) was calculated as the quotient of the relative frequency of sensitization and the relative frequency of use. Results. The SEQs varied greatly, offering a ranking regarding risk of sensitization: phenoxyethanol (SEQ: 0.06), benzyl alcohol (0.30), parabens (0.35), sorbates (0.92), benzoates (1.35), formaldehyde-releasers (1.6), methylisothiazolinone (MI) (1.7), iodopropynyl butylcarbamate (3.4), methylchloroisothiazolinone/MI (9.0), and 2-bromo-2-nitropropane-1,3-diol (13). There was a good correlation between the ranking of substances according to potency (hazard) and the ranking of the SEQ (risk). Conclusion. High frequencies of sensitization may be put into perspective by the frequent use of certain preservatives. Despite infrequent use, others (with higher potencies or too high use concentrations) may turn out to be associated with an increased risk. Hazard assessment should be supplemented by risk assessment.