Coal tar is a liquid by-product of the distillation process that turns coal into coke. It has long been used in products used in the treatment of skin complaints such as dandruff and psoriasis. It is also known to kill head lice when used as a shampoo.

Not all coal tar shampoos are equal when it comes to head lice. To effectively kill head lice you need to use an extra strength coal tar shampoo. Most "normal" strength brands have a 0.5% coal tar content. You'll need something stronger so read the labels. The strongest types are often referred to as being "therapeutic".

To kill head lice simply use the coal tar shampoo as normal but the lather on for 15 to 30 minutes. Then rinse through thoroughly. Use a nit comb afterwards to comb through the wet hair. Do this for three consecutive days. Then use twice a week after that with daily combing until the head lice have completely gone.

Some parents claim that by using the shampoo once a week their children seem less prone to being reinfected by head lice. Others use the shampoo as a precaution whenever they receive a head lice letter from school even if their children don't already have an infestation.

Is coal tar safe to use as a head lice remover? In high concentrations (over 5%) coal tar is a known carcinogen. Therapeutic strength shampoos can contain concentrations of 2.5% and some now carry a warning about the carcinogenic properties of coal tar on the label.

But the risk is very small risk. The National Psoriasis Foundation claims coal tar is a "valuable, safe and inexpensive treatment option" and coal tar products have been used for a very long time. There is feeling that the benefits far outweigh the small risks involved. All over the counter head lice shampoos come with a health risk attached. Coal tar is no different but coal tar is an effective way to kill head lice, it has been used safely for many years and should have negligible risk when used only occasionally.