But some doctors are growing anxious about this trend, pointing out that herbal remedies, too, can have adverse effects.
John Simpson, chair of a national working party on head lice, says that none of the herbal remedies has been tested in clinical trials and that concentrated or essential oils could have toxic side-effects. "Rosemary is already known to trigger uterine contractions and miscarriage," he points out. "Just because something is natural doesn't necessarily mean it is safe. These oils are used in high concentrations, and we don't know enough about their toxicity."
Christine Steward, president of the National Institute of Medical Herbalists, is scathing in her response. "It's a joke, when you consider that they are putting pesticides on children's heads," she says.
Ms Steward, who favours a mix of rosemary, lavender, eucalyptus and geranium oils for head lice, concedes that essential oils should always be diluted rather than used neat on the skin because some are irritants. Nor should more powerful oils such as thyme be used.
"You have to be careful what you are doing, but used properly the oils are fine," she says. "I know there have been no clinical trials, but many of these oils are known to have antimicrobial properties."
Rinsing a child's hair in rosemary tea will also deter lice from crossing from one head to another, she adds.
So what should parents do if they suspect an infestation? First, relax: head lice rarely cause serious health problems, although they can itch horribly. And forget about any social stigma associated with poor hygiene: lice have no preference for either clean or dirty hair.
For a firm diagnosis, comb wet hair with a fine-tooth comb, working carefully downwards from the top of the head and round. The presence of a live louse - colour grey-brown, and about the size of a sesame seed - is unmistakable; nits (the dead egg cases, which go white after hatching) are not.
There is more than one treatment option. Chemical head lice lotions, available in chemists, contain either malathion, an organophosphate, carbaryl (now regarded as a potential human carcinogen, and available on prescription only) or pyrethroids such as permethrin. All these have been shown to be effective in clinical trials, although resistance can build up; two applications are usually needed, one week apart, to allow for any unhatched lice.
But could they be toxic? Among farmers, organophosphates have been linked to symptoms such as chronic fatigue, memory loss and flu-like symptoms such as sweating and dizziness. Research has also shown, rather alarmingly, that if a child is treated with 0.5 per cent malathion lotion - the normal solution - the amount absorbed is above that absorbed by protected insecticide workers.
However, this is still well below acute toxicity levels, and malathion is quickly metabolised by the liver and excreted in the urine. Reassuringly, trials on adult volunteers of a single application 10 times normal strength did not cause any adverse effects.
The risks associated with the recommended dose of malathion are thought to be very low. More worrying is when parents continually treat their children with insecticides, or use them at intervals of less than a week, which can increase the risk of side-effects.
Those who opt for a herbal treatment should dilute it in a carrier oil such as sunflower or almond oil, rather than use it direct on to the skin. The solution should be rubbed into dry hair and the head towel-wrapped for an hour, before washing out.
A third method of eliminating head lice is known to have absolutely no side-effects. Called "bug busting", it involves using shampoo, conditioner, a special comb - and a fair amount of patience - to break the life cycle of the lice. Although there have been no trials of this method, many have reported success. Treatment packs are available from chemists; or ring Community Hygiene Concern on 0181-341 7167 for more details.