Validation of a questionnaire algorithm based on repeated open application testing with the constituents of fragrance...

In a European study on contact allergy in the general population, it was hypothesized that the combination of contact allergy to a fragrance together with a history indicating dermatitis at exposure, and thereafter subsequent avoidance of scented products, implied a diagnosis of allergic contact dermatitis.

The primary aim of this study was to validate this hypothesis and algorithm. The secondary aim was to investigate whether there was any association between the outcome of the repeated open application test (ROAT) and the patch test reactivity.

In total, 109 patients with and without contact allergy to fragrance mix (FM) I were recruited. Volunteers from six European dermatology clinics participated in the study including a patch test and a ROAT.

Positive ROAT reactions were noted in 26 of the 44 volunteers with contact allergy to FM I. None of the volunteers reacted to the vehicle (P < 0·001). More individuals with a positive algorithm had positive ROATs than those with a negative algorithm. However, the difference was not statistically significant. The lower the patch test concentration eliciting a positive test reaction, the more likely a positive ROAT and the more likely that the positive ROAT appeared early during the investigative period.

The algorithm used in this study was not substantiated in this ROAT set-up. The stronger the patch test reactivity the more likely was a positive ROAT and the more likely it was that the positive ROAT appeared early during the application period. What's already known about this topic? To the best of our knowledge, a scientifically designed and conducted repeated open application test (ROAT) has never been performed before to validate a diagnosis of allergic contact dermatitis partly based on a questionnaire. What does this study add? This is the largest controlled, randomized and blinded ROAT performed to date. Higher patch test reactivity to fragrance mix I indicated a greater likelihood of a positive ROAT. What are the clinical implications of this work? Further refinement of the questions is required in order to diagnose allergic contact dermatitis from fragrances based on a questionnaire.