It is well known in government health circles that ministers receive more mail about one child health topic than any other. Meningitis? Concerns over the side-effects of vaccination? The possibility of power lines causing leukaemia? Actually, no - it's head lice.

Pediculus humanus capitis, while unpleasant, is relatively harmless to human health, yet the merest mention of this tiny insect sends most parents rushing hysterically to the chemist. In 1995, some six million treatments were sold at a cost of pounds 14m, yet only around 60,000 cases of head lice occur each year. Our heads may tell us lice are no respecters of cleanliness or social class, but our hearts cannot give up the age- old stigma that equates them with squalor and filth.

Like it or not, head lice are a fact of childhood. Ten per cent of primary school children play host to them at any one time, with socially "promiscuous" seven- to 12-year-olds most at risk. Left untreated, lice commonly infect whole families, who may be blissfully unaware of their blood-guzzling guests. Contrary to popular misconception, most people with lice do not itch.

Although severe infestations can cause low-grade allergies and flu-like symptoms, many people now question whether conventional cures are worse than the disease.

Panic first set in in November 1995, when the government Committee on the Safety of Medicines decided to withdraw all lotions containing the insecticide carbaryl from over-the-counter sales, after experiments on mice and rats revealed a potential cancer risk to humans. Carbaryl-based treatments are now available on prescription only.

More recently, attention has focused on malathion, the organophosphate pesticide that achieved notoriety by implication in Gulf war syndrome and in the ill-health of farmers exposed to sheep-dip. Community Hygiene Concern (CHC), a charity that seeks to protect the public from potentially toxic treatments, is concerned that the chemical, available in over-the- counter treatments, may be absorbed through the scalp and thereby affect the body's immune system.

However, CHC is more worried about other over-the-counter head-lice treatments that contain the insecticide pyrethroids, permethrin and phenothrin. In 1991, the US Environmental Protection Agency classified permethrin as a possible human carcinogen on the basis of animal testing; CHC says that there is evidence that the chemicals can interfere with the hormone and reproductive systems.

Groups like CHC and the Pesticide Exposure Group of Sufferers argue that no levels of pesticides are safe. Both claim to have received many reports of poisoning from head-lice treatments, with symptoms including headaches, dizziness, hyperactivity, hallucinations, panic attacks and depression. CHC is particularly worried about the potential effect of such pesticides on pregnant and breastfeeding women, and the possible longer-term impact on human fertility.

But treatment manufacturers and many health professionals believe such concerns have been blown out of all proportion to real risk, pointing out that like all medicines, head-lice treatments are continuously monitored for safety. The Medical Entomology Centre at Cambridge describes malathion as exceptionally safe, and in 40 years of use there are no reports of carbaryl leading to cancer in humans - the experiments that prompted its withdrawal from general sale used large doses over prolonged periods, creating far higher levels of exposure than those relating to intermittent use of head-lice preparations.

Nevertheless, even those convinced of the safety of head-lice products warn against their common abuse. The Medical Entomology Centre, for instance, recommends that no treatment is used more than three times over a three- week period. Parents also should check with a GP which pesticide is currently recommended, as many health authorities rotate products in an attempt to combat the resistance of lice to standard preparations.

While natural remedies for head lice using quassia chips or essential oils abound, these can be difficult to use effectively, and in some cases can be toxic in high concentrations. The Department of Health and many authorities have opted instead to promote the CHC's Bug Busting programme as a first-line treatment. With good information and some determination, this wet-combing method can eliminate infection within a fortnight using ordinary shampoo, conditioner and a fine-toothed plastic comb to break the louse's life cycle.

For a Bug Buster kit and booklet on the wet-combing method contact: Community Hygiene Concern, 160 Inderwick Road, London N8 9JT, or call 0181-341 7167.