A closer look at Coal Tar and Salicylic Acid
Over-the-counter (OTC) Topicals how do they work? Let’s take a deeper dive into OTC treatments and what they can do for you.
OTC topicals are available in pharmacies, drugstores, supermarkets or directly from the manufacturer without a doctor’s prescription. They come in many different forms. Two active ingredients, salicylic acid and tar, are approved by the FDA as treatments for psoriasis.
Salicylic acid is classified as a keratolytic, or peeling agent, and works by causing the outer layer of skin to shed. It is a common and effective treatment for a wide variety of skin problems. As a psoriasis treatment, it acts as a scale lifter, helping to soften and remove psoriasis scales.
Strong salicylic acid preparations can cause irritation if left in contact with the skin for too long. The body may absorb too much salicylic acid if used over large areas of the skin. Salicylic acid may also weaken hair shafts and make them more likely to break, leading to temporary hair loss.
Tar derived from both coal and wood (e.g., juniper, pine) are both used for medicinal purposes. However, coal tar is the type used most commonly to treat psoriasis. Tar can help slow the rapid growth of skin cells and restore the skin’s appearance. In addition, it can help reduce the inflammation, itching and scaling of psoriasis. Tar products can vary dramatically from brand to brand. Generally, the higher the concentration of tar, the more potent the product.
Tar can irritate, redden and dry the skin. Test a tar product on a small area of the skin first. If reddening occurs, try applying the tar on top of a moisturizer. Tar can stain clothing, bed linen, and light-colored hair. Tar makes skin more sensitive to sunlight, so be sure to wash it off thoroughly, use sunscreen and monitor your sun exposure. Tar remains active on the skin for at least 24 hours, and you are at increased risk of sunburn during this period.
Studies show some of the chemicals in coal tar may cause cancer, but only in very high concentrations, such as in what is used in industrial paving. Anyone using tar regularly should follow a regular skin cancer checkup schedule. California requires OTC coal tar shampoos, lotions and creams that contain more than 0.5 percent coal tar to be labeled with cancer warnings. However, the FDA maintains that OTC products with coal tar concentrations between 0.5 percent and 5 percent are safe and effective for psoriasis, and there is no scientific evidence that the tar in OTC products is carcinogenic.
Other OTC Treatment
There are other products which don’t contain salicylic acid or coal tar that are beneficial for treating psoriasis. Ingredients such as aloe vera, jojoba, zinc pyrithione, capsaicin and others, are frequently used to moisturize, soothe, remove scale or relieve itching.
The effectiveness of some of these products is not known. Be aware that “natural” ingredients can also cause side effects or allergic reactions. If irritation occurs, discontinue use.
Inverse psoriasis can be treated with Castederm, a liquid that is painted on the affected skin to help to dry moist lesions of psoriasis in folds of the body. The use of powders may also help to dry the moist lesions associated with inverse psoriasis.
Keeping the skin lubricated on a daily basis is an important part of psoriasis care because it reduces redness and itching and helps the skin heal. Dermatologists recommend heavy creams and ointments to lock water into the skin. Cooking oils and even shortening can be effective as economical substitutes for commercial moisturizers. Here are some quick tips for keeping your skin moisturized:
- use fragrance-free products
- apply moisturizers after showering and after washing your hands
- wash with moisturizing soaps
- limit your lukewarm showers to 10 minutes or less
Bath solutions can be beneficial in treating psoriasis. Adding oil, oilated oatmeal, Epsom salts or Dead Sea salts in a bath can help remove psoriasis scale and soothe itching. Soak for around 15 minutes and apply a moisturizer or oil to the skin immediately after getting out of the bath.
Scale lifters (keratolytics)
Scale lifters help loosen and remove scale allowing medications to reach the psoriasis lesions. There are scale-lifting products designed for the scalp, body or both. Note that scalp products are usually stronger and may be too harsh for other skin sites. OTC products that contain an active ingredient of salicylic acid, lactic acid, urea or phenol can be used as scale lifters.
Some topical medications or moisturizers can be occluded (or covered) to increase their effectiveness and the amount absorbed into the skin. With occlusion, the topical is applied to psoriasis lesions and the area is covered with plastic wrap, cellophane, waterproof dressing, cotton socks or a nylon suit. Always check with your doctor before occluding a steroid or other prescription medication.
There are several ingredients that have been approved by the U.S. Food and Drug Administration (FDA) for treating itch. Some of these include calamine, hydrocortisone (a weak steroid), camphor, diphenhydramine hydrochloride (HCl), benzocaine and menthol. Beware that these ingredients may increase irritation and dryness.