The guinea pig maximization test was used to determine the potential of seven cannabinoids to produce allergic contact dermatitis. delta 9-Tetrahydrocannabinol and cannabinol were found to be extreme (Grade V) sensitizers. Cannabidiol, delta 8-tetrahydrocannabinol, and cannabichromene were moderate (Grade III) sensitizers. Cannabigerol and cannabinol methyl ether were not sensitizers. Most of the cannabinoids were found to be allergenically cross-reactive. Additionally, it was shown that the presence of a free 1'-hydroxyl group was required for sensitization, but not to elicit a response in sensitive animals.