Of the common childhood disorders, few are met with such revulsion in adults as head lice (Pediculus hummus capitis), or nits. They are an increasing menace in schools, and some parents are so squeamish about them that they can hardly bring themselves to treat the problem.
Many take it as a comment on their own standards of hygiene if their child becomes infested but in reality hygiene, or at least cleanliness, rarely has anything to do with it head lice.
A lousy condition
Nits are parasites that live in the hair and scalp, and need human blood to survive. Spread through direct contact, they can infest anyone, regardless of how 'clean' they are.
In fact, clean, grease-free hair that hasn't been treated with artificial chemicals or stripped of its natural oils is easier for nits to grab hold of.
In fact, nits are head-lice eggs. They are attached firmly to the hair shaft and are often mistaken for dandruff. They are oval and usually yellow to white in colour. The nits hatch into nymphs or immature-adult head lice in about seven days. On reaching maturity, adult lice can live up to 30 days on a person's head and lay up to 100 eggs a month.
An adult louse is about the size of a sesame seed, has six legs and is tan to greyish-white, but will look darker in dark hair.
Infestation with head lice is a very common problem in the UK, especially among school children. The lice cannot fly or jump or hop. Instead they transfer to from one head to another by walking along strands of hair.
The lice pass from one person to another during direct head-to-head contact so children whispering secrets at school or families enjoying a cuddle at home provide head lice with head-to-head contact necessary to allow them to travel from one head to another.
In the UK, four pesticides are used to treat head lice; regulatory authorities and some medical scientists believe they are 'safe', though this belief is hotly disputed.
Carbaryl has been available by prescription only for more than a decade, since studies found it caused cancer when given to rats in large doses throughout their lives. It is generally considered a last resort treatment for stubborn cases of infestation.
Over the counter you can buy products that contain the organophosphate insecticide malathion (Derbac-M liquid, Prioderm cream shampoo, Prioderm lotion, Quellada-M cream shampoo and Quellada-M liquid); permethrin (Lyclear Creme Rinse) and phenothrin (Full Marks liquid and lotion).
Malathion is the same stuff used for sheep dip. Like carbaryl it works by blocking an enzyme called cholinesterase. In humans this can cause such side effects as headache, nausea, paralysis, chest pain, muscular twitch, blurred vision, cramps, giddiness, impaired memory and disorientation, dizziness, tremulousness and hallucinations. Chronic exposure has been linked to chronic fatigue and fibromyalgia.
These serious long-term reactions are most common in people who have been exposed to these pesticides over the long-term, such as farmers. But, given their high toxicity and children's greater sensitivity to toxic chemicals, it is appropriate to question their use as occasionally head lice treatments too.
Permethrin and phenothrin are pyrethroid insecticides. Permethrins are irritating to the skin and eyes and can also worsen allergies and asthma. Human studies are scarce, but animal studies suggest they can suppress the immune system and be toxic to the liver. This type of pesticide is implicated in Gulf War veterans' disabilities. Pregnant and breastfeeding women should not use permethrins, and they are likely to have a greater toxic effect in young children. For a comprehensive review on permethrin see this link.
There is strong evidence that licensed treatments claiming to kill lice and nits in a single application don't. Over the years, head lice have developed treatment resistance, leading to the formulation of ever stronger mixtures. What is more, most chemical treatments don't kill the eggs, which then go on to hatch within a week or so, starting a whole new cycle of infestation.
Repeated treatments and the use of one pesticide treatment after another on the same child has also become more common. As a result, many parents report that conventional treatments give their children acute headaches. Others, including parents, experience rashes and more severe allergic reactions from using them.
Products such as Hedrin lotion, Itax lotion and NYDA pump spray contain either dimethicone or cyclomethicone. Because they are film formers, silicones are associated with skin irritation. Silicone-based products work in a different way to conventional insecticides, and in fact it is their film forming ability that makes them effective against lice.
Instead of paralysing their central nervous systems they kill the lice by physically coating their bodies and suffocating them. Because of the way these products work, head lice cannot become resistant to silicones. The problem is silicone-based lotions don't kill eggs, so you need to repeat treatment after seven days to kill any lice that have hatched from eggs since the first application.
At the more natural end of the scale there are now many so-called non-toxic products on the market which makes use of natural essential oils such as tea tree and neem and which are either simple ‘wash and go' type shampoos or leave-in treatments. These may make removing eggs easier but they don't kill eggs either so treatments need to be repeated until all eggs and lice are gone from the hair.
The usual suspects
Some shampoo-in treatments, even the ‘natural' ones contain all the usual harsh ingredients that this column has criticised in the past, such as sodium lauryl sulphate (SLS, a harsh cleanser often used as an engine de-greaser which is irritating to skin and mucous membranes) and cocamide DEA (irritating the skin; belongs to a family of fatty acids called alkanolamines, which are considered hormone-disrupters).
Apart from silicones, leave-in solutions can contain triethanolamine (a skin and eye irritant and suspected hormone-disrupter), propylene glycol (irritating to eyes, skin and respiratory tract and a penetration enhancer, altering skin structure, allowing other more toxic chemicals to penetrate more deeply into the skin and eventually the bloodstream). Many contain the whole range of hormone disrupting parabens preservatives: methyl-, butyl-, ethyl- and propyl-paraben.
In truth, neither the conventional synthetic pesticides nor the 'natural' alternatives that are currently in use are fully effective against head lice and their eggs. In other words there is nothing you can simply spray or rub into your child's head that will do the job for you so that you won't have to get too up close and personal with your child's lice.
The most natural treatment: 'bug busting'
The best way to see if your child is infested is to look and if you find your child has nits, manually removing them is just one of those little jobs that as a parent you simply have to face up to. Nits are easiest to see because they are 'glued' to the hair shaft. Nymphs and adults are harder to find, and can move quickly away from searching eyes and fingers.
The best and most natural treatment for nits is what is known as the wet combing or ‘bug busting' method. It requires no chemicals, produces no resistance and is a very thorough and effective way to remove eggs, nymphs and adults lice. Here's what you do:
• wash the hair as normal using an ordinary shampoo
• apply non-toxic conditioner liberally to wet hair (this causes the lice to lose their grip on the hair)
• comb the hair through with a normal comb first
• with a fine tooth nit comb, comb from the roots along the complete length of the hair and after each stroke check the comb for lice and wipe it clean. Work methodically over the whole head for at least 30 minutes
• rinse the hair and dry
• repeat every three days for at least two weeks
Ultimately, it's not the 'stuff' you put on the hair, but how conscientious you are at combing it out afterwards that will really win the day against head lice.
Pat Thomas is a former editor of the Ecologist
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