Encyclopedia · anti dandruff
Coal tar
One of the oldest dandruff and psoriasis treatments; it works, but it contains carcinogens, smells, stains and is no longer anyone's first choice.
What it is
Coal tar is a by-product of coal processing, used in shampoos at about 0.5-5% for dandruff, seborrheic dermatitis and psoriasis. Rules on tar in cosmetics differ between regions, so check the label.
How it works
Review summaries credit anti-inflammatory, antibacterial, anti-itch and cell-division-slowing effects (Roelofzen 2007).
What the studies show
- A double-blind randomized trial compared a tar shampoo with a non-tar shampoo (salicylic acid, piroctone olamine, elubiol). The non-tar shampoo was as effective as tar and better at lowering Malassezia counts (Pierard-Franchimont 2000).
- A review lists short-term effects of coal tar as folliculitis, irritation and contact allergy. Coal tar contains carcinogens, shown in animal and occupational studies, but patient studies show no clear increase in skin or internal tumours, and better epidemiology is needed (Roelofzen 2007).
Side effects and safety
Irritation, folliculitis, contact allergy, sun sensitivity, staining of light hair and clothing, and a strong odour. Carcinogenicity is established in animals and occupational exposure, while patient data are inconclusive. Avoid it in pregnancy unless a doctor advises otherwise, and do not use it on broken skin.
Bottom line
Reserve coal tar for scalp psoriasis or stubborn scale when other options fail, and then only with a clinician's guidance. Modern non-tar combinations performed as well in the one head-to-head we found. Discuss with a doctor.
Studies 2
Piérard-Franchimont C et al. Comparative anti-dandruff efficacy between a tar and a non-tar shampoo. Dermatology. 2000
Tested: salicylic acid plus piroctone olamine plus elubiol shampoo versus coal tar shampoo (double-blind)
Result: The non-tar combination was at least as effective as tar and lowered Malassezia counts.
Read the study ↗Roelofzen JH et al. Coal tar in dermatology. J Dermatolog Treat. 2007
Result: Coal tar has anti-inflammatory, antibacterial, anti-itch and antimitotic effects; short-term harms are folliculitis, irritation and contact allergy; it contains carcinogens shown in animal and occupational studies, though patient data show no clear increase in tumours.
Read the study ↗Related
- Salicylic acidA scale-loosening ingredient that helps thick flakes and scalp psoriasis plaques and works best paired with an antifungal.
- Selenium sulfideAn old, inexpensive anti-dandruff active that new trials suggest works about as well as ketoconazole and has been tested across all curl types.
- KetoconazoleAn antifungal shampoo ingredient that is among the best-proven treatments for dandruff and, with much weaker evidence, a possible add-on for pattern hair loss.
- Scalp psoriasisScalp psoriasis is an autoimmune skin condition that needs medical treatment, not just a stronger shampoo, and good options exist from topical steroids to biologics.