Coal Tar for Psoriasis: How It Works and What the Evidence Shows

Coal tar has been used to treat psoriasis for over 100 years, and despite newer treatment options, it remains genuinely effective — with a safety record that's held up surprisingly well under scrutiny. Here's the full picture.

How Coal Tar Works

Coal tar contains polycyclic aromatic hydrocarbons, and research suggests its anti-psoriatic effect works largely through activation of the aryl hydrocarbon receptor (AhR), which helps normalize the excessive skin cell turnover and suppress inflammatory pathways involved in psoriasis. The exact mechanism is still being fully characterized, but this AhR-related pathway is the same one that newer medications like tapinarof are specifically designed to target — meaning modern pharmaceutical research has, in a sense, validated the biological logic behind a century-old remedy.

The Evidence for Effectiveness

Coal tar has strong evidence behind it, including notably long remission periods compared to some other treatments. It's particularly well-studied for scalp psoriasis — relevant given that roughly 80% of psoriasis cases involve the scalp. The Goeckerman regimen (coal tar combined with UVB phototherapy) has produced particularly strong results historically: one retrospective study in children with moderate-to-severe psoriasis found 85% of patients achieved more than 80% plaque clearance, comparable to adult outcomes with the same treatment.

For palmoplantar psoriasis specifically — one of the harder-to-treat presentations we've covered separately — coal tar combined with a topical corticosteroid has shown particular promise in clearing difficult plaques.

The Safety Question, Addressed Directly

Coal tar's biggest reputational issue is the cancer concern, since pure coal tar does contain carcinogenic compounds. It's worth being precise about what the actual evidence shows: safety concerns are largely based on studies of industrial, occupational exposure — people working directly with coal tar at far higher concentrations than the roughly 5%-or-less concentrations used in psoriasis products. Multiple retrospective studies following patients treated with coal tar and UVB decades earlier found no increased skin cancer risk after 25 years of follow-up. The American Academy of Dermatology notes there is currently no evidence that coal tar at the concentrations used for psoriasis causes cancer in humans.

The genuine caution point: coal tar does increase skin's sensitivity to UV light, so sun protection matters, and it shouldn't be combined with UV phototherapy or tanning beds without medical guidance.

Practical Considerations

  • Common side effects are mostly cosmetic and mild — skin irritation, a distinctive smell, and staining of light-colored fabric or hair
  • Patch test first, particularly if you have sensitive skin
  • Avoid during pregnancy or breastfeeding — there isn't enough research on effects in these situations to confirm safety
  • Combine with sun protection, given the increased UV sensitivity

Frequently Asked Questions

Does coal tar cause cancer?

The evidence at the concentrations used in psoriasis products doesn't support this concern — cancer risk data comes primarily from much higher occupational exposure, and long-term follow-up studies of psoriasis patients treated with coal tar found no increased skin cancer risk.

Is coal tar better than newer treatments?

It's not necessarily "better," but it remains a genuinely effective, low-cost option with notably long remission periods — a real consideration for anyone weighing treatment options, particularly for scalp or palmoplantar psoriasis.

Next Steps

Explore our full scalp psoriasis collection.

This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis, or treatment.

Sources & References

Back to blog

Leave a comment