Small, flat, wingless, grey parasites about 2mm long with strong claw legs and which feed on human blood. There are two distinct forms of this sort of louse – the head louse and the clothing or body louse, but they are similar in appearance.
The pearly, oval eggs or “nits” stick to hairs or fibres of clothing and the nymphs moult three times before maturing, feeding as they go. The life cycle takes about 18 days. Past epidemics of typhus and trench fever transmitted by lice are now unlikely, but irritating bites can produce impetigo and similar afflictions.
Having lice does not necessarily imply that one is dirty, but the sooner treatment is sought, and the source eliminated, the better.