Overview
Also known as pediculosis capitis or ‘nits’, head lice describes a parasitic insect infection of the scalp by Pediculus capitis, which feeds on the scalp’s blood supply. It is commonly seen in children.
Pathophysiology
Eggs are laid close to the scalp surface and may appear similarly to dandruff. ‘Nits’ often describe hatched shells with no lice present as they remain attached to the hair and turn white. Nymphs are white baby lice that hatch and mature into adult lice which can be up to 3 mm in size and are tan to grey. They feed on the scalp’s blood supply. These lice are completely dependent on humans for nutrition and warmth and once detached, they can only survive for around 2 days.
Transmission
The transmission requires head-to-head contact. They cannot jump, fly, or swim, are not transmitted by pets, and are unlikely to be transmitted by sharing hats, pillows, towels etc. (however, hair that is caught in a brush may risk transmitting head lice).
Epidemiology
- Head lice can affect all ages, however, it is most common in children aged 4-11 years old
- Head lice are more common in girls than boys
Diagnosis
Affected people may have itching, however, a live louse must be found to confirm an active infestation. This can be done via fine-toothed combing of wet/dry hair and sticking lice to tape.
All household members and close contacts should also be checked for head lice.
Management
Overview
Treatment is only indicated if living lice are present and includes wet combing (e.g. the Bug Buster® kit, which is available on the NHS). Other options include insecticides as:
- Physical insecticides that coat lice and suffocate them such as dimeticone
- Chemical insecticides that poison lice such as malathion
School exclusion is not necessary and household members and close contacts are only treated if they have an active infection as well.
Complications
Pruritic rash in surrounding areas – often the back of the neck and behind the ears due to a hypersensitivity reaction to louse faeces. This may also cause red papules, lymphadenopathy, and erythema with a honey-coloured crust on the scalp.
Psychosocial problems – such as stigma, anxiety, distress, loss of sleep, and missing school.
Secondary bacterial infection – rare, but can lead to impetigo and cellulitis
Prognosis
- If untreated, head lice infestations can persist for long periods and increase the likelihood of complications
