Susceptibility to primary irritants: age dependence and relation to contact allergic reactions.

Patch tests with three primary irritants were performed in 600 persons with eczema and in 33 healthy controls, The irritants assayed were: croton oil (20%) in mineral oil, thymoquinone (1%) in ethanol and crotonaldehyde (7.5%) plus sodium lauryl sulphate (4%) in aqua dest. The number of positive reactions to croton oil was found to decrease with age, while for thymoquinone and crotonaldehyde and for the total irritant score no age dependence was observed. No significant correlation was found between sensitization to common contact allergens and susceptibility to irritants. The incidence of positive reactions to common allergens proved to increase with age.