Tar soap is sometimes recommended to relieve psoriasis symptoms such as itching, inflammation, and scaling. The two types of tar soap used to treat psoriasis are pine tar soap and coal tar soap.
Pine tar soap is made from pine tree resins and has a strong pine scent. It’s still used by some people to treat psoriasis, but doctors who support tar soap as a treatment are more likely to recommend coal tar soap. Coal tar is a distillation byproduct of coal processing. It’s made of thousands of compounds that may vary depending on preparation.
Coal tar has been used to treat skin conditions since ancient times. For over 100 years, it has been used to treat psoriasis.
Historically, over-the-counter coal tar soap contained coal tar byproducts such as polycyclic aromatic hydrocarbons (PAHs). Today, true coal tar soap is hard to get without a prescription.
You can still purchase pine tar soap that contains pine tar and pine tar oils without a prescription. For example, you can get Packers Pine Tar Soap, which claims to be effective against psoriasis. Its formula has remained consistent since it was first created in 1869. The Army Corps of Engineers also used it as an insect repellent during World War II.
The goal of any psoriasis treatment is to slow the growth of skin cells to reduce inflammation and plaque formation, and remove scales. Coal tar soap seems to be effective at reducing scaling, itching, and inflammation. It has few side effects, although exactly how it works isn’t clear. The National Psoriasis Foundation indicates coal tar helps slow skin cell growth and improves skin’s appearance.
Coal tar treatments may be combined with other therapies such as topical corticosteroids or ultraviolet B light. The Goeckerman regimen is a therapy that combines coal tar and ultraviolet light. It’s considered to be a very effective against severe psoriasis. The treatment requires daily sessions for up to four weeks and can be messy. Despite its success, not all people living with psoriasis want to deal with the mess and commitment. Some people seek other treatment options.
An evidence-based review published in the Journal of Drugs in Dermatology found that most studies support the use of coal tar preparations to treat psoriasis and atopic dermatitis. The review also reports the level of evidence was weak and that larger, more controlled studies are needed.
Coal tar soap is generally well tolerated, but it may cause negative side effects such as:
- skin irritation or redness
- sensitivity to sunlight
In addition to being messy, coal tar soap has a strong, unpleasant odor, and easily stains light-colored hair, clothes, and bedding.
Whether coal tar products cause cancer has been hotly debated. When studies indicated occupational exposure to coal tar may cause cancer, it raised concerns that topical use might be carcinogenic as well. In 2010, a study published in the Journal of Investigative Dermatology seemed to put the debate to rest. The study didn’t observe an increased risk of cancer with the use of coal tar soap. It also noted that coal tar soap could be considered a safe dermatological practice treatment for psoriasis and eczema.
In addition to tar soap, other over-the-counter treatments exist. Most over-the-counter psoriasis treatments are used to moisturize and soothe skin, remove scales, and relieve itching. These include:
- aloe vera
- zinc pyrithione
- oilated oatmeal
- Epsom salts or Dead Sea salts
- anti-itch products such as calamine, hydrocortisone, camphor, and menthol
Occlusion, the process of covering an applied topical medication with plastic wrap, cellophane, or other covering, is sometimes used to increase a product’s effectiveness.
Talk to your doctor before using tar soap to treat psoriasis. They’ll tell you the proper amount to use and how often you should use the soap. If you experience the symptoms of an allergic reaction while using tar soap, seek medical help immediately. Those symptoms may include:
- difficulty breathing
- chest tightness
If the treated area becomes red, itchy, or irritated, or your symptoms worsen or don’t improve, call your doctor as soon as possible.