Evolving Surfactant Trends in the Thai Personal Care Market Over 15 Years and Their Association with Clinical Patch Test Reactivity.

BACKGROUND: Surfactants in personal care products are an established trigger of allergic contact dermatitis. However, regional data comparing market usage with sensitization rates remain limited. OBJECTIVES: To examine 15-year trends in Thai surfactant prevalence and correlate them with clinical patch test reactivity. METHODS: Surfactant prevalence in 6864 personal care products was surveyed using the Thai Contact Allergen Avoidance Program database (2010-2024). Concurrently, patch test results from 6603 patients were analyzed across 3 5-year intervals. RESULTS: Cocamidopropyl betaine (CAPB) was the most prevalent surfactant overall (20.3%) and in cleansers (43.2%), whereas polysorbates predominated in non-cleansing formulations (17.9%). In cleansers, use of CAPB (P < 0.001), glucosides (P = 0.009), and cetrimonium chloride (P < 0.001) rose over time. Cetrimonium bromide, benzalkonium chloride, and CAPB showed the highest patch test positivity rates. Conversely, positivity declined for CAPB (P < 0.001), benzalkonium chloride (P = 0.007), lauryl glucoside (P = 0.019), and cocamide diethanolamine (P < 0.001). CONCLUSIONS: The Thai market is shifting toward milder surfactants. A paradoxical decline in CAPB and lauryl glucoside sensitization occurred despite their rising prevalence. Continuous market monitoring is essential to keep patch test series and patient counseling relevant.