Assessment of the risk of fragrance allergy in the general population: challenges and methodological issues.

There are still unanswered questions about the safety of fragrances. In this conference paper, fragrance allergy will be considered in the context of a wider discussion concerning the prevalence and causes of contact dermatitis. No criteria for a reliable diagnosis of 'contact dermatitis' are available. International recommendations and standardization for the patch test method exist; however, the question of whether agents that are positive are causally linked to contact dermatitis remains fraught with uncertainties concerning false-positive rates and clinical relevance. Most of the discussion concerning prevalence or incidence variations of allergic contact dermatitis to fragrances concentrate on the frequency of positive patch tests in clinical series, i.e. 'floating numerators'. Risk assessment requires that data from different sources are integrated and compared. Therefore, both a 'sentinel surveillance' system and more refined epidemiological studies in well defined populations are needed to reliably assess risks associated with fragrance exposure.