Coal tar in different forms can treat several skin conditions. It may cause some side effects, while certain treatments require that they carry a cancer warning in some locations. However, experts generally consider it safe to use.
People use coal tar to treat skin conditions such as psoriasis and eczema. It can also help reduce inflammation, scaling, and itching.
Crude coal tar has a strong and unpleasant smell — dermatologists do not often use it. However, people can find a more refined version of the product in shampoos, creams, gels, soaks, and lotions.
Dermatologists usually prescribe coal tar products in conjunction with other treatments. Several coal tar treatments can be very effective — some people have reported skin symptoms clearing completely, including long remissions without psoriasis.
This article explores what coal tar is, which conditions it treats, how to use it, and whether it can cause cancer.
Coal tar is a by-product of bituminous coal, or black coal, which contains a tar-like substance called bitumen, or asphalt.
Dermatologists prescribe coal tar to patients with skin conditions, such as eczema or psoriasis, to reduce redness, itching, and inflammation.
Skin care specialists may still use the substance in its crude form to treat people with chronic plaque psoriasis. In these situations, they may prescribe a 2–5% coal tar in an emollient base using dressings and in combination with UV radiation therapy.
People with difficult-to-treat psoriasis on their soles or palms may benefit from coal tar treatments. Dermatologists may also prescribe it to individuals with scalp psoriasis.
The effectiveness of coal tar treatments varies, and a person cannot tell how effective a product will be simply from the amount of coal tar it contains. One study found that patients using a lotion containing 1% coal tar extract had better results than people using a lotion with 5% coal tar extract.
A person can consult with a dermatologist for product recommendations if they wish to use coal tar.
Dermatologists may prescribe coal tar treatments alone or as part of a treatment plan that includes phototherapy, other medications, or both.
Coal tar may be effective in treating:
- scalp psoriasis
- plaque-type psoriasis
- psoriasis on soles and palms
- thickened skin
Coal tar products come in a variety of topical forms. A person may use them in lotion, ointment, cream, gel, bath soaks, and shampoo.
If an individual is using a coal tar treatment on their body, they should apply and massage it into their skin. A dermatologist will advise on how often a person needs to do this.
Wrapping the area after applying the treatment increases the strength of coal tar, but a person will find optimal results from following their dermatologist’s instructions. When using a coal tar shampoo, individuals should make sure it gets on to their scalp.
Dermatologists may use tar and extracts of crude coal tar in the treatment of chronic eczema.
Dermatologists generally regard coal tar as safe, but it may cause:
- skin irritation
- rashes or acne-like breakout
- unpleasant odor
- stinging or burning
- dry or brittle hair
- stains on light-colored hair and clothing
- sun sensitivity
- worsening of psoriasis
Dermatologists have been prescribing coal tar for over 100 years to treat psoriasis, so experts generally consider it to be safe. However, in some places, such as California, coal tar products need to carry a cancer warning.
Authorities required manufacturers to add this notice due to animal studies, where researchers exposed animals to far higher amounts of coal tar than people would normally use to treat psoriasis.
The cancer warning is also partly based on previous research into occupational studies focusing on individuals working with coal tar.
However, researchers have found no evidence to suggest that coal tar with a concentration of between 0.5 and 5% causes cancer.
Some studies have found that certain ingredients in coal tar can cause cancer if a person becomes exposed to very high concentrations, such as during paving roads or roofing.
People who are sensitive to the sun or take medicine that makes them more susceptible to UV light should not use coal tar.
Coal tar is a by-product of bituminous coal. Although people rarely use it in its crude form, dermatologists may prescribe products containing refined coal tar for psoriasis or eczema.
Coal tar can effectively treat symptoms of skin conditions, including itching, inflammation, thickened skin, and hard-to-treat sole and palm psoriasis. People can also use it as a topical treatment.
However, coal tar may have side effects, including unpleasant odor, skin irritation, rashes, swelling, burning or stinging, sun sensitivity, stains, and dry and brittle hair.
Studies show that coal tar may cause cancer after exposure to very high concentrations of the substance. However, experts generally consider the amount of coal tar in psoriasis and eczema treatments to be safe.