Coal tar
Coal tar has been used for centuries for its anti-inflammatory and analgesic effects. Oral administration for central effects is now rare as coal tar also contains a range of dangerous and carcinogenic compounds, and does not allow for the administration of standardized doses, although some doctors readily utilize coal tar preparations for topical administration (ex. Denorex, Psoriasin) in the treatment of skin conditions such as eczema and atopic dermatitis. Many modern analgesics and anti-inflammatory agents (ex. paracetamol, and its previously used predecessor phenacetin) are derived from compounds which were originally discovered during studies to elucidate the chemicals responsible for the tars reputed health benefits.