Background: Cheilitis is an inflammatory condition of the lips. Its causes can be exogenous (irritants, allergens), endogenous (atopic dermatitis, systemic disorders) or unknown.Objectives: To determine the prevalence of allergic contact cheilitis (ACC), its risk factors, and common allergens in patients with cheilitis at a Thai university-based tertiary care hospital.Methods: A retrospective chart review was conducted on patients with cheilitis referred for patch testing between January 2007 and December 2021.Results: Among 5366 patients referred for patch testing, 410 (7.6%) had cheilitis. ACC was diagnosed in 32% of the cheilitis patients. Compared to non-ACC cases, the patients with ACC were more likely to be young and female and have a disease duration of <3 months, no underlying disease and a white-collar job (p-value <0.05). The most common contact allergens were patient's products (73.3%), nickel sulfate (29.8%), potassium dichromate (14.5%), castor oil (14.3%) and benzalkonium chloride (13.0%). Lip cosmetics and toothpastes were major ACC sources.Conclusions: ACC should be considered in cheilitis patients, especially in patients with specific risk factors. Castor oil is an emerging allergen. Patch testing using commercial allergen series and patients' own products is crucial for identifying causative agents. The development of a specific cheilitis series is warranted.
