Irritant Contact Dermatitis Risk of Common Topical Traditional Chinese Medicines Used for Skin-Lightening: A Pilot Clinical Trial with 30 Volunteers

Topical traditional Chinese medicine- (TTCM-) related contact dermatitis is not uncommon but ignored. Patch and photopatch tests using 6 individual herbal ingredients and Bai-Zhi-Kao (BZK; 白 芷 膏), a skin-lightening TTCM preparation, were conducted on 30 participants. Twenty-five subjects showed at least 1 positive reaction, including 6 (20.0%) participants who reacted to BZK. The majority reacted to Radix Ampelopsis japonica (Bai-Lian; 白 蘞) (60.0%), whereas few reacted to Rhizoma Bletilla striata (Bai-Ji; 白 芨) (16.7%), Rhizoma Atractylodis macrocephalae (Bai-Zhu; 白 朮) (10.0%), Radix Angelicae dahuricae (Bai-Zhi; 白 芷) (3.3%), and Herba asari (Xi-Xin; 細 辛) (3.3%). In the photopatch test, 3 participants (10.0%) reacted positively to BZK and 10 to ≥1 constituent; however, all reacted to Radix Angelicae dahuricae (26.7%), Radix Ampelopsis japonica (13.3%), and Rhizoma Bletilla striata (3.3%). In contrast, no subjects showed positive reactions to Sclerotium Poria cocos (Bai-Fu-Ling; 白 茯 苓). Thus, BZK and its constituents might present potential latent risk of contact dermatitis owing to the possible presence of Radix Ampelopsis japonica and Radix Angelicae dahuricae. Furthermore, TTCMs, particularly cosmetic products, must be used carefully, with ample warning of potential contact dermatitis risk.