Studies show some of the chemicals in coal tar may cause cancer, but only in very high concentrations, such as in what is used in industrial paving. Anyone using tar regularly should follow a regular skin cancer checkup schedule. California requires OTC coal tar shampoos, lotions and creams that contain more than percent coal tar to be labeled with cancer warnings. However, the FDA maintains that OTC products with coal tar concentrations between percent and 5 percent are safe and effective for psoriasis, and there is no scientific evidence that the tar in OTC products is carcinogenic.
Consumers should follow the Drug Facts label and consult with their health care providers if their symptoms do not improve. The drug should be applied once daily in a thin layer on the affected areas of skin, and it is for external use only. Differin Gel % should not be used on damaged skin (for example, cuts, abrasions, eczema, or sunburn). People using Differin Gel % should avoid sunburn and avoid product contact with their eyes, lips and mouth. Differin Gel % should not be used by people who are allergic to the product. In the first few weeks of use, skin may become irritated (redness, itching, dryness, burning). Consumers should stop use and ask a doctor if irritation becomes severe, if there is no improvement in acne after three months of daily use, if symptoms of allergic reaction appear, or if they become pregnant or are planning to become pregnant while using the drug.