Topical

A topical product is one applied to the surface of the skin, where its ingredients act locally in the outer layers rather than being designed to enter the bloodstream.

The category includes creams, lotions, balms, salves, gels, oils, patches, and sprays. The outer layer of skin, the stratum corneum, is an effective barrier, and most compounds applied topically remain in or near it; how far an ingredient penetrates depends on its molecular size, fat solubility, the vehicle it is dissolved in, and whether penetration enhancers are used. Topical is distinct from transdermal, which describes formulations specifically engineered to move a compound through the skin into systemic circulation.

Topical cannabinoid products are widely sold and are regulated as cosmetics unless drug claims are made. Cannabidiol is fat-soluble and penetrates the skin poorly in most simple formulations, and studies measuring blood levels after ordinary topical use have generally found little or no systemic absorption. Research on cannabinoids applied to the skin has been mostly preclinical and small in scale. Labels should state the cannabinoid content per container and link to a certificate of analysis.