The exact mechanism of action is unknown. Coal tar is a complex mixture of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds.
It is a keratolytic agent, which reduces the
growth rate of skin cells and softens the skin's keratin.
Coal tar is used in medicated shampoo, soap and ointment. It demonstrates antifungal, anti-inflammatory, anti-itch, and antiparasitic properties. It may be applied topically as a treatment for dandruff and psoriasis, and to kill and repel head lice. It may be used in combination with ultraviolet light therapy.
Coal tar is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Coal tar is generally available as a generic medication and over the counter. In the United Kingdom 125 ml of 5% shampoo costs the NHS about £1.89. In the United States a month of treatment costs less than $25 USD.
Pine tar has historically also been used for this purpose. Though it is frequently cited online as having been banned as a medical product by the FDA due to a "lack of evidence having been submitted for proof of effectiveness", pine tar is included in the Code of Federal Regulations, subchapter D: Drugs for Human Use, as an OTC treatment for "Dandruff/seborrheic dermatitis/psoriasis".
Coal tar may be used in two forms: crude coal tar (Latin: pix carbonis)
or a coal tar solution (Latin: liquor picis carbonis, LPC) also known as
liquor carbonis detergens (LCD). Named brands include Denorex, Balnetar,
Psoriasin, Tegrin, T/Gel, and Neutar. When used in the extemporaneous
preparation of topical medications, it is supplied in the form of coal tar
topical solution USP, which consists of a 20% w/v solution of
coal tar in alcohol, with an additional 5% w/v of polysorbate 80 USP;
this must then be diluted in an ointment base such as petrolatum.
In animal studies, coal tar has been shown to increase the chance of skin cancer.
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Other side effects not listed may also occur in some
patients. If you notice any other effects, check with your healthcare
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
If you miss a dose of this medicine, apply it as soon as
possible. However, if it is almost time for your next dose, skip the missed
dose and go back to your regular dosing schedule.
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Certain medicines should not be used at or around the time
of eating food or eating certain types of food since interactions may occur.
Using alcohol or tobacco with certain medicines may also cause interactions to
occur. Discuss with your healthcare professional the use of your medicine with
food, alcohol, or tobacco.
Use this medicine only as directed. Do not use more of it and do not use it more often than recommended on the label, unless otherwise directed by your doctor. To do so may increase the chance of side effects.
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Coal tar products should not be used on infants, unless otherwise directed by your doctor. Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of this medicine in children with use in other age groups.
Many medicines have not been studied specifically in older
people. Therefore, it may not be known whether they work exactly the same way
they do in younger adults or if they cause different side effects or problems
in older people. There is no specific information comparing use of this
medicine in the elderly with use in other age groups.