Choose the proper vehicle

In a case study from May 1992, a 34-year-old man with androgenic alopecia experienced suspected allergic contact dermatitis of the scalp after using a topical minoxidil solution ('Rogaine'), which contained 60% alcohol and propylene glycol. Patch testing revealed that the man did not have a reaction to minoxidil in alcohol or petrolatum, but did react to the 'Rogaine' solution and minoxidil in propylene glycol. This led to the diagnosis of vehicle-dependent allergic contact dermatitis. The study concluded that patch testing should include minoxidil in various vehicles, such as propylene glycol, alcohol, and water, to diagnose vehicle-dependent allergic contact dermatitis and to find an appropriate formulation that excludes the irritating substance.