The classroom is a playground for all sorts of bugs and lurgies, but for many teachers, catching Pediculus humanus capitis, head lice, is enemy Number One. If you haven't had them crawling around your head yet, chances are that you soon will. So...
What do they look like?
Head lice (nits) are greybrown wingless insects with six legs, two eyes, two antennae, and six hooks in their mouths. Given the chance, they will grow to about 2-4 mm long. The eggs are white, translucent and the size of a pin-point. They are laid near the base of hair shafts, where they stick resolutely, moving outward as the hair grows. It takes between six and 10 days for the eggs to hatch and only a week for the larvae to become sexually mature adults. Empty eggs remain attached to the hair shaft.
How do you catch them?
Most lice are caught through head-to-head contact, but can also be passed on by sharing hairbrushes, combs, hats, headphones and towels.
How do I know if I've got them?
During their lifecycle, head lice deposit their faeces in the scalp. It is an allergic reaction to these, rather than movement on the head, which causes the itching commonly associated with infestation. A rash, which is often worse behind the ears or on the back of the neck, may also appear.
Other signs include nits stuck to the hairs as they grow out, and louse droppings, which look like a fine black powder. Check your pillows and sheets each morning if you're collecting evidence.
What is the best way to diagnose head lice?
Put your head under a bright light, wet and section your hair, and inspect each piece. White bits that are brushed off are dead skin scales, not nits.
How do I get rid of them?
Thinking, talking or reading about nits is enough to make anyone's head itch. There are several ways. You can buy a number of insecticides, available as shampoos, lotions, liquids or cream rinses, over the counter at a chemist or through your doctor. However, today's "super nit" is increasingly resistant to these products and not everyone relishes the thought of using insecticides on themselves. Investment in a nit comb might be wise. Wet your hair, apply conditioner, then comb it thoroughly every third or fourth day over a two-week period. The aim is to remove all live lice and eggs until none are left. There is an "alternative" treatment, which involves using lotions or sprays that contain herbs, or oils such as tea tree oil. However, scientific evidence of their efficacy is thin.
Who do I tell?
Your headteacher, family, friends... and anyone else you've been in close contact with. All cases of head lice need to be treated, or you never get rid of them. Your school will most certainly have a policy on notification and treatment of head lice.
THAT'S LICE: 14 CREEPY FACTS
* Having head lice is not a sign of poverty or poor hygiene.
* All heads of hair - dirty or clean - are equally attractive to lice.
* Cases of lice are most common in children aged three to 10, but can occur at any age.
* Lice are spread from person to person when heads touch.
* Louse eggs, which are white, translucent and the size of a pinpoint, are called nits.
* Nits stick tightly to the side of hair shafts which makes them difficult to remove.
* There are three choices of treatment: insecticides, combing, and alternative treatments, including those containing essential oils and herbal extracts.
* All individuals who may be affected by an outbreak need to be treated.
* No-one has ever died from head lice.
* The mouth of a louse has six hooks by which it attaches itself to the skin of the scalp for feeding.
* Saliva is injected into the scalp through two needle-like tubes. The juices prevent blood from clotting and the tubes provide the method of transportation from scalp to mouth.
* The translucent bodies of lice turn reddish brown when engorged with blood.
* The life of a louse depends entirely on the blood extracted from humans.
* A louse will starve to death after 55 hours without blood.