Coal tar typically takes 2 to 8 weeks to produce noticeable improvement, depending on the severity of your condition and how you’re using it. Most people see some reduction in scaling, redness, and itching within the first few weeks, but full clearing can take longer.
What to Expect in the First Few Weeks
Coal tar doesn’t work like a moisturizer or a steroid cream that provides fast, visible relief. It works by slowing down the overproduction of skin cells. In psoriasis, skin cells multiply far too quickly, piling up into thick, scaly plaques. Coal tar suppresses the DNA machinery that drives this overproduction, gradually reducing the net rate at which new skin cells form. Interestingly, at the very start of treatment, coal tar actually causes a brief increase in skin cell activity before its slowing effect takes over and the thickened skin begins to thin out.
Because of this mechanism, patience matters. In clinical cases using a 2% coal tar foam applied twice daily, patients with plaque psoriasis on the scalp saw significant improvement in scaling, redness, and plaque thickness after just two weeks, with continued improvement over the following four weeks. For plaques on the palms and underarms, significant clearing took closer to eight weeks of consistent twice-daily use, with near-complete clearing and only residual darkening of the skin left behind.
Timelines by Condition and Product Type
The speed of results depends heavily on what you’re treating and which form of coal tar you’re using.
- Scalp psoriasis or seborrheic dermatitis (shampoo): Coal tar shampoos are typically used twice a week. You can expect a noticeable reduction in flaking and itching within 2 to 4 weeks of regular use.
- Body psoriasis (creams, ointments, foams): Applied once or twice daily, these tend to show meaningful improvement within 4 to 8 weeks. Thicker plaques on areas like the palms or elbows may take the full 8 weeks.
- Coal tar baths: Used anywhere from daily to once every three days, soaking for 10 to 20 minutes per session. The usual treatment course lasts 30 to 45 days.
Over-the-counter coal tar products in the U.S. range from 0.5% to 5% concentration. Lower concentrations still work but may take longer to show results. Higher concentrations are more potent but also more likely to irritate the skin.
Coal Tar Combined With UV Light
If your dermatologist recommends combining coal tar with ultraviolet B (UVB) light therapy, a protocol known as the Goeckerman regimen, results tend to come faster and last longer. Coal tar acts as a photosensitizer, making the skin more responsive to UV light. The two treatments together produce better results than either one alone, and remissions can last as long as 12 months. In this approach, coal tar is applied once or twice daily, at bedtime or at least 30 to 60 minutes before UV exposure, then fully removed before the light session.
How to Use It for Best Results
Consistency is the single biggest factor in how quickly coal tar works. Skipping applications or using it sporadically will delay results significantly. For body treatments, apply once or twice daily as directed. For shampoos, lather into wet hair, massage thoroughly into the scalp, rinse, and repeat the process. Once your condition is under control, you can often reduce application to two or three times a week for maintenance.
Coal tar is considered safe for long-term use. Dermatologists have prescribed it for over a century, and the American Academy of Dermatology lists long-term use as one of its specific advantages over other psoriasis treatments. It also costs less than most alternatives, which makes it practical as an ongoing maintenance option.
Side Effects That Can Slow Progress
A common side effect is tar folliculitis, small inflamed bumps around hair follicles, especially on the legs. This happens more often with concentrations above 2% and is caused by a chlorine-containing component in the tar that irritates follicles. If folliculitis develops, it can force you to reduce the frequency of application or switch to a lower concentration, which naturally extends the timeline to see results.
Acne-like breakouts can also occur, though they differ from regular acne and are triggered by a different chemical in the tar. Skin staining and a strong odor are cosmetic downsides that don’t affect how well the treatment works but do lead some people to stop using it prematurely.
Sun Sensitivity After Application
Coal tar makes your skin significantly more sensitive to sunlight, and this effect lasts at least 30 hours after you remove the product. During this window, you’re more prone to sunburn and a stinging “smarting” reaction from UV exposure. If you’re using coal tar on exposed skin, plan your sun exposure accordingly or use sun protection. Getting a bad sunburn on treated skin won’t just hurt; it can worsen the very condition you’re trying to treat and set back your progress.