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Coal tar, one ingredient in OTC dandruff products, is a

byproduct of treated bituminous coal. In constant exposure to

concentrated solutions in industrial settings over long periods ([SIZE=3]20

to 25 years[/SIZE]), coal tar has been associated with skin cancer. But

coal-tar products are considered [SIZE=3]safe for topical use in shampoos[/SIZE]because contact with the scalp is only for a short duration.

For body seborrheic dermatitis and psoriasis, however,

products containing coal tar remain on the skin for longer periods.

There are no well-defined, long-term studies that demonstrate how

long coal-tar products can be used safely. FDA has noted that

prolonged use of such products may not be completely risk free due

to possible cancer-causing effects.