Coal tar has been used for more than a century to treat psoriasis and is still used today by dermatologists in combination with other psoriasis treatments. It is a safe, effective, and inexpensive form of treatment that can help slow the rapid growth of skin cells that give rise to scaly, itchy plaques on the skin.

In the United States, coal tar is available over the counter in creams, gels, lotions, oil, and shampoos, typically at concentrations of between 0.5% and 5%.

Coal tar was first discovered around 1665 and used for medical purposes as early as the 1800s. It is included on the World Health Organization’s List of Essential Medicines and is “generally recognized as safe” by the U.S. Food and Drug Administration (FDA).

This article describes the different coal tar products for psoriasis, including how they are used and the possible risks and side effects.

Coal Tar Products for Psoriasis

Coal tar is found in many over-the-counter (OTC) products, including creams, gels, lotions, oils, and bath additives. Coal tar shampoos are also available for scalp psoriasis.

Compound pharmacists who customize medications can mix crude coal tar (which has a black, paste-like texture) or an alcohol-based coal tar solution with all sorts of bases, including steroid creams and ointments.

OTC coal tar products include:

  • Betatar gel shampooCutar emulsion cream and shampooDenorex medicated dandruff shampooDHS Tar lotion and shampooDoak Tar lotion and shampooDuplex T lotion and shampooFototar creamIonil-T Plus shampooMG 217 moisturizing creamNeutrogena TDerm oilNeutrogena TGel gel

Unlike products of the past that were universally black and tarry, many newer formulations are non-staining and washable.

How to Use Coal Tar for Psoriasis

Coal tar is intended for external use only. Lotions, gels, oils, creams, and shampoos can be applied directly to the affected skin and left on for between one to two hours. (This can vary based on the concentration of coal tar in the product. Read the product label for precise instructions.)

Take special care when applying coal tar to the face; avoid getting any into the eyes, nostrils, or mouth. The same applies to the genitals or rectum. If you accidentally get coal tar in the eyes or other delicate tissues, rinse thoroughly with cool water for 15 minutes.

Coal tar products intended for baths or foot soaks should be mixed thoroughly and used for around 10 to 15 minutes. Take extra care when using coal tar in bathtubs or showers as it can make surfaces slippery.

Results can vary, but adults will usually see a visible response to treatment within four weeks. In children, the response tends to be quicker, more along the lines of two weeks. (For safety, coal tar should only be used in children under the direction of a dermatologist.)

Coal tar can be used on its own or in combination with other treatments, including topical corticosteroids (steroids) or phototherapy (a treatment for various skin conditions using artificial ultraviolet light).

Effectiveness of Coal Tar for Psoriasis

The effectiveness of coal tar can vary from one person to the next. For some people, coal tar can completely clear psoriasis and achieve long-term remission. Others may not respond as well.

Coal Tar and Phototherapy

Coal tar is sometimes used with phototherapy to make the skin more receptive to ultraviolet (UV) radiation. This should only be performed by a dermatologist using specialized phototherapy equipment. Never use a tanning bed or tanning lamp to treat psoriasis as it is more likely to cause skin damage or trigger a flare.

Moreover, the concentration of coal tar in a product does not influence how well it works. A 1% coal tar solution may work as well as a 5% solution, and a 5% solution may end up causing more side effects.

Coal tar belongs to a class of drugs called keratoplastics, which also include skin medications like benzoyl peroxide, tretinoin, and salicylic acid.

Coal tar works by slowing the turnover rate of skin cells. This is the process in which new skin cells move to the surface of the skin to replace old ones. With psoriasis, the turnover rate is increased, causing the cells to “pile up” on the surface of the skin.

By slowing this process, coal tar can help reduce scaling, flaking, and itching while decreasing the size of plaques.

Coal tar is especially useful in treating scalp psoriasis and hard-to-treat palmoplantar psoriasis (psoriasis of the palms and soles).

Side Effects of Coal Tar

OTC coal tar products are considered safe when used in concentrations between 0.5% and 5%. Even so, the products can still cause side effects, particularly on delicate skin and at higher concentrations.

What Research Says

A 2016 review from the Cochrane Database of Systemic Reviews reported that 33% of people treated with coal tar shampoo experienced an improvement in scalp psoriasis symptoms but did not have a significant reduction in plaque size. Even so, coal tar caused fewer side effects than other topical products and may be beneficial when used in combination with other psoriasis treatments.

Common side effects of coal tar include:

  • Skin irritation
  • Skin dryness
  • Itchiness
  • Burning or stinging
  • Dry and brittle hair
  • Photosensitivity (extreme sensitivity to the sun)
  • Unpleasant, lingering odor
  • Rash

Many of these side effects can be minimized by applying moisturizer before and after the coal tar treatment.

Allergic reactions are rare but can occur. If you are prone to allergies, test the product on a small patch of skin and wait 24 hours to see if a rash develops.

There are also no known drug interactions associated with coal tar.

Treatment Considerations

Coal tar preparations should never be applied to inflamed, broken, or infected skin. Doing so may cause pain and trigger a flare-up of symptoms.

Can Coal Tar Make Psoriasis Worse?

As effective as coal tar can be in treating psoriasis, it can also make psoriasis worse in some people, according to the American Academy of Dermatology. You should stop treatment immediately if you develop severe burning or stinging, swelling, or worsening psoriasis.

It is important to note that coal tar photosensitivity can persist for up to 24 hours after application. To avoid sunburn, wash your skin thoroughly after treatment and apply a high-SPF sunscreen if you plan to be outdoors. Do not use tanning beds.

Some coal tar preparations can stain clothes, towels, bedding, and even light-colored hair. To better avoid this, apply the preparation in the shower and wash and rinse thoroughly afterward. Any hair discoloration will usually return to normal after a few shampoos.

Coal tar products made with liquor carbonis distillate (LCD) are less likely to cause staining.

What to Look For

There are literally hundreds of coal tar preparations found on drugstore shelves and online. Like most OTC products, they are not strictly regulated by the FDA.

To ensure safety and purity, opt for products that have undergone testing with an independent certifying body like the U.S. Pharmacopeia (USP), NSF International, or ConsumerLab. That way, you’ll know whether the product contains the ingredients listed on the label at the listed potency level.