Is Coal Tar Shampoo Good for Hair Loss? Evidence Review

Illustration of a coal-tar preparation, shampoo and scalp teaching model.

Short answer: Coal tar has clinical evidence for controlling dandruff, but its reputation as a DHT-blocking hair-loss treatment comes from a very different source: a patent describing a leave-on lotion. Looking at what each source actually measured makes the distinction clearer.

Where Did the Coal-Tar “DHT Blocker” Claim Come From?

A 1997 patent proposed that liquor carbonis detergens, a coal-tar preparation, could interfere with the conversion of testosterone into DHT. Its formulation also contained salicylic acid, camphor, castor oil and alcohol. This was a lotion left on the scalp, rather than a shampoo rinsed away.

The patent describes two people: a 47-year-old woman who reported improvement over six months, and a 48-year-old man who reported less shedding after switching from minoxidil. Those accounts are interesting historical observations, but there was no comparison group, blinded hair count or reported scalp-DHT measurement. With several ingredients in the lotion, the accounts cannot identify which ingredient contributed to any improvement. Read the original patent and its two case examples.

What Happened When Coal Tar Shampoo Was Tested for Dandruff?

Illustration of three unbranded shampoos with a scalp model and magnifying lens.

A randomized, double-blind study enrolled 60 volunteers with moderate to marked dandruff. Over four weeks, researchers compared a 0.5% coal-tar shampoo with a non-tar formula containing salicylic acid, piroctone olamine and elubiol.

Clinical ratings and participants’ assessments found similar dandruff control, and both products received approval ratings of at least 70%. More detailed measurements favored the non-tar formula for reducing Malassezia yeast counts during treatment and limiting the return of scaling afterward. These were human scalp results, but the researchers were measuring dandruff—not hair regrowth or DHT. Read the 60-person shampoo comparison.

What Is Coal Tar Shampoo Actually Intended to Treat?

The published DHS Tar label lists control of itching and flaking associated with dandruff, seborrheic dermatitis and psoriasis. It gives the shampoo a defined scalp-care role. Neither these labelled uses nor the dandruff trial establishes the patent’s proposed anti-DHT mechanism or shows that the shampoo reverses follicle miniaturization.

The label also warns about increased sensitivity to sunlight and possible discoloration of some hair colours. Read the published coal-tar shampoo label and its warnings.

Which Shampoo Studies Actually Measured Shedding or Hair Counts?

That is the useful next comparison. A reduction in visible flakes, fewer shed hairs during washing and an increase in scalp hair density are different outcomes. A study can show progress on one without showing progress on the others.

Our shampoo evidence comparison looks at studies of ketoconazole, piroctone olamine and zinc pyrithione, including the actual changes in shedding, strand thickness and visible hair counts.