Coal Tar
In plain terms
A traditional treatment for psoriasis, dandruff, and seborrhea, and also a known carcinogen. The catch is the dose and purpose: short, doctor-guided use on a skin condition is FDA-approved and looks low-risk, while daily long-term or cosmetic use of a carcinogen is not worth it.
What the evidence shows
Coal tar is a thick, dark by-product of processing coal, used for over a century to calm psoriasis, dandruff, and seborrheic dermatitis because it slows the overgrowth of skin cells. It is also a recognized carcinogen: coal tars are an International Agency for Research on Cancer Group 1 known human carcinogen, the highest certainty level, on the strength of occupational cancers, and it carries hundreds of polycyclic aromatic hydrocarbons, many carcinogenic on their own. That is why it sits on California's Proposition 65 cancer list and why the European Union bans it from cosmetics outright. And yet the picture has a real other side: the US FDA keeps coal tar as an approved over-the-counter treatment for dandruff and psoriasis at 0.5 to 5 percent, and the largest human study of patients treated with it, a dermatology cohort, found no increased cancer risk from therapeutic skin use. The cancers show up at industrial and occupational exposures far above what a medicated shampoo delivers. So this is a depends, set by dose and purpose. For someone treating real psoriasis or stubborn dandruff, short or supervised courses are an FDA-backed option with reassuring human data. What is not worth it is reaching for a carcinogen daily, long-term, or for ordinary cosmetic reasons when gentler options like piroctone olamine and salicylic acid exist. It also makes skin more sensitive to sun, so sun protection matters during use.
On the label
Listed as coal tar or coal tar solution, in medicated shampoos and creams. If you are treating psoriasis or seborrhea, use it as directed or with a dermatologist and protect treated skin from sun. For everyday dandruff, gentler actives like piroctone olamine are a lower-risk first try.