Allergie acute contact dermatitis due to Arnica tincture self-medication.

After repeated intermittent use of Arnica tincture for rosacea a 66-year-old patient developed acute allergic contact dermatitis with blistering upon the single application of Arnica tincture to the dorsum of the right hand for minor swelling. Contact allergy of the delayed type to Arnica tincture could be proven by patch testing. Early diagnosis and treatment prevented exacerbation and spreading of the disease. In view of the wide use of Arnica preparations, particularly for self-medication, and the notable sensitizing potential, Arnica tincture should be a regular component of patch test series, at least when drug allergy is suspected.