Tar soap is sometimes recommended to relieve psoriasis symptoms, like 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.
In the past, over-the-counter (OTC) coal tar soap contained coal tar byproducts, like polycyclic aromatic hydrocarbons (PAHs). Today, true coal tar soap is hard to get without a prescription.
You can still buy pine tar soap that contains pine tar and pine tar oils without a prescription. Some brands for sale today have been in production since the 1800s and use the same formula.
The goal of psoriasis treatment is to slow the growth of skin cells to reduce inflammation and plaque formation, and remove scales.
Coal tar soap might be helpful in reducing scaling, itching, and inflammation. It has few side effects, although exactly how it works isn’t clear.
According to the National Psoriasis Foundation, coal tar helps slow skin cell growth and improves skin’s appearance.
The Goeckerman regimen is a therapy that combines coal tar and ultraviolet light. It’s considered to be effective for relieving moderate to severe psoriasis symptoms. But the treatment isn’t right for everyone. Goeckerman requires daily sessions for up to four weeks and can be messy.
An evidence-based review published in the found that most studies support the use of coal tar preparations to treat psoriasis and atopic dermatitis. But it 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 unpleasant side effects:
- 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 suggested 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 treatment for psoriasis and eczema.
In addition to tar soap, other OTC treatments are available. Most OTC 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 [Affiliate link:] 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 can give you tips on how much soap to use and how often.
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.
Tar soap might be helpful in easing some psoriasis symptoms. It can also be used as part of a combination treatment.
But the soap may cause skin irritation, including an allergic reaction, so it’s a good idea to talk to your doctor before adding it to your treatment plan.