The atrophogenic effect of crude coal tar on human epidermis.

The effects of crude coal tar on human epidermis were studied in fourteen healthy young adult males. A 20% reduction in viable epidermal thickness, as determined by computer assisted analytical microscopy, was observed after 40 days of topical treatment. Prior to this long term effect of crude coal tar, an initial transient hyperplasia was observed during the first 2 weeks of treatment. These findings indicate that crude coal tar by itself can act as a cytostatic agent on normal human skin, when applied intensively.