Wonderful stuff is coal tar.
Not only does it burn with a greater calorific value than standard coal, but it also can be processed and formed into a haircare product, along with other fossil fuel derivatives.
Polytar, developed and produced by Stiefel Laboratories, Inc., is just that hair care product. It is a specialist shampoo designed for the treatment of eczema, psoriasis, persistent dandruff and other lovely conditions of the scalp. It is available from most outlets of Boots and what have you, and is available in both standard and "AF" varieties. The "AF" variety is a prescription-only version, I believe, which is marketed in Europe under the name "Fongitar" (I kid you not) for more severe conditions.
The stuff itself is gloopy, brown, and smells like diesel fuel. In fact, that probably constitutes one of its active ingredients. Don't accidentally get any in your mouth either. It tastes truly foul. After two days' substitution of it for my usual L'Oreal products due to a dearth of the latter (I have big hair) my hair felt dried out and a bit dead rather. Needless to say, though, any dandruff, itching, or flaky scalp I could possibly have had didn't stand a chance.
I believe my father uses this stuff almost exclusively. He swears by it. If I had his rapidly receding hairline and encroaching greyness (and was still yet to breach 50) I would swear by it too!