Chemsex refers to the intentional use of psychoactive substances to enhance, explore, or alter sexual experiences. The use of geolocation apps, and its link with physical, psychological, and social harms for the individual as well as society has been described ‘Polydrug use’—combining multiple substances to amplify or diversify effects—is frequently reported across these groups. This article provides a comprehensive overview of the sexual effects of substances commonly used in chemsex contexts. We introduce the Ph…