Coal tar shampoo is a keratolytic agent, meaning it softens the skin protein keratin. This makes it easier to remove thickened, dead, dry skin cells. Coal tar shampoo is effective at relieving skin dryness, flaking, itching, redness and scaling caused by eczema, psoriasis and seborrhea, according to Drugs.com. It also helps prevent the overly rapid growth of skin cells that occurs in psoriasis and seborrheic dermatitis, and it can help with dandruff. Some side effects are possible with this shampoo.
Skin Irritation
Skin irritation is possible when using coal tar shampoo, according to Drugs.com. Some people experience burning or stinging sensations, itching, redness, swelling or tenderness. Stop using coal tar shampoo and consult with your doctor if you develop severe skin burning, stinging or swelling.
Photosensitivity
Coal tar shampoo may cause increased sensitivity to the sun, a condition known as photosensitivity, which can raise your risk of severe sunburn. Brigham and Women's Hospital advises avoiding sun exposure for at least 24 hours after using coal tar products unless your health-care practitioner says it's OK. If you do go out in the sunlight, wear protective clothing and apply sunscreen. Additionally, you shouldn't have exposure to a sunlamp or tanning booth while using coal tar shampoo.
Allergic Reaction
Some people may experience an allergic reaction to coal tar products. According to Drugs.com, signs include a rash, hives, trouble breathing, tightness in the chest, and facial or mouth swelling. An allergic reaction to coal tar shampoo should be considered a medical emergency, because it may lead to life-threatening anaphylaxis.
Considerations for Women
Women who are pregnant or planning to become pregnant should talk with a doctor before using coal tar shampoo, because the active ingredient could harm an unborn baby, according to Drugs.com. Additionally, coal tar may transfer into breast milk, so breastfeeding mothers also should consult a doctor before using this shampoo.
Staining
The American Academy of Dermatologists notes that coal tar stains "just about everything it touches." Although the product is effective and usually does not cause serious side effects, this factor and its unpleasant odor tend to make people look for other solutions for their skin problems. Coal tar can temporarily stain skin and nails, and if you get it on fabric, permanent stains may result. Coal tar shampoo also can temporarily discolor blond, gray or colored hair, but this staining should wash out after you wash your hair with another product a few times.