Cinnamic aldehyde in toothpaste. 1. Clinical aspects and patch tests.

Although cinnamon is known to cause dermatitis in bakers and confectioners, it has only rarely been reported as causing trouble in food or cosmetics. A newly-formulated 'spicy' toothpaste containing cinnamon as a flavouring agent was the cause of oral symptoms in eight patients referred to clinics in Buckinghamshire and in Malmö and in a further eight patients discovered subsequently. Similar symptoms and patch test results were observed independently at both centres. Positive reactions were obtained with 1% cinnamic aldehyde in 15 out of 16 patients tested. Only one patient reacted to a standard sample of balsam of Peru (25% in petrolatum).