Contact Dermatitis: a Common Adverse Reaction to Topical Traditional Chinese Medicine

Background: Over the past decade, there has been an increase in the use of topical traditional Chinese medicine (TTCM). The most common adverse event seen in the use of TTCM is contact dermatitis. This retrospective study was designed to determine the types of commonly used TTCM in Singapore causing contact dermatitis.

Methods: We retrospectively reviewed the case notes of 10 patients seen at the National Skin Centre over a 4-month period with a diagnosis of adverse cutaneous reactions to TTCMs.

Results: A total of 10 patients were diagnosed with contact dermatitis to TTCM at our institution over a 4-month period. The clinical manifestation ranged from eczematous lesions to urticarial plaques and blisters. Five of these patients were patch-tested to our standard series, our in-house TTCM series, as well as to the TTCM they had used. The other five patients declined patch testing. The results of patch testing confirmed the diagnosis of allergic contact dermatitis in three of the tested patients. Negative patch testing results inferred the diagnosis of irritant contact dermatitis to TTCM in the other two patients. Two of the patients with positive patch tests also had a positive reaction to balsam of peru and fragrance mix. The three positive patch tests were all caused by medicated oils.

Conclusions: These results suggest it is likely that essential oils present as constituents of the medicated oils could be the possible allergen. The study also confirms that contact dermatitis is a common adverse event associated with the use of TTCM.