Coal tar products are available as shampoos, creams, gels, ointments, and soaps. They can help slow skin growth and reduce inflammation, itching, and scaling. To apply a coal tar shampoo, massage it into the scalp and leave on five to 10 minutes before rinsing out. You can leave other tar products on overnight. Staining and odor are the main drawbacks. A non-medicated conditioner after shampooing can help against the odor of tar shampoo.