Used primarily as an antifungal agent in skin care products, particularly for treating fungal skin infections such as ringworm, athlete's foot, and other dermatophyte infections. It is commonly formulated into creams, ointments, or powders for external topical application. Calcium undecylenate inhibits the growth of fungi and helps prevent reinfection. Additionally, it is used in some cosmetics and pharmaceuticals as a preservative to control unwanted microbial growth.