• Use detection combing (systematic combing of wet or dry hair with a detection comb) to confirm the presence of lice.
• Wet combing takes 5–15 minutes per head; lice are immobilized by hair conditioner, so are easy to see on the comb.
• Dry combing takes 3–5 minutes per head. Using a comb on dry hair may produce static; when a louse is spotted on the comb, placing a thumb on it before drawing the comb out of the hair prevents the louse being flicked off the comb by static.
• Lice found using detection combing at home can be attached to sticky tape and brought to the consultation to aid diagnosis.
• Advise the person (or the child's parent) that all members of the household should also be checked.
• Only make a diagnosis of active head lice infestation if a live head louse is found.
• An itching scalp is not sufficient to diagnose active infestation.
• Itching can persist for days to weeks after successful eradication of head lice.
• Itching may not develop for several weeks or months after becoming infested.
• Itching is a common reaction to hearing that there are head lice within the school or community.
• The presence of nits alone (eggs) does not indicate active infestation. They are commonly misdiagnosed. See Differential diagnosis.

These recommendations are based on guidelines from the Public Health Medicine Environmental Group [PHMEG, 2008].

Detection combing

• Detection combing (on dry or wet hair) is recommended because there is evidence to show that both methods are more effective and more reliable than direct visual inspection (by parting the hair).
• Choice will depend on personal preference.

Itching is not sufficient to diagnose active head lice infestation.

• Itching is caused by a delayed hypersensitivity reaction to louse saliva and may persist after the eradication of head lice [Ibarra, 1998; HPA, 2008; PHMEG, 2008].

Nits alone are not sufficient to diagnose active head lice infestation.

• Eggs glued to hairs, whether hatched (nits) or unhatched, are not proof of active infestation, because it is difficult to distinguish between dead and live eggs with the naked eye, and eggs may retain a viable appearance for weeks after death [Ibarra, 1998; Burgess, 2006].

• Itching
• Psychogenic itch on hearing that there are head lice within the school.
• Other itchy scalp conditions, such as eczema.
• Successfully treated head lice infestation but with persisting itch; itch can persist from days to weeks after successful eradication.
• Nits
• Nits can be confused with:
• Seborrhoeic scales.
• Hair muffs (secretions from the hair follicle that are wrapped round the hair shaft).
• Hair spray.
• Nits can be distinguished from seborrhoeic scales, hair muffs, and hair spray by brushing the hair:
• Nits stick firmly to the hair even after vigorous brushing.
• Seborrhoeic scales, hair muffs, and hair spray can be brushed off.
• Lice
• Head lice might be confused with pubic lice (Phthirus pubis) or body lice (Pediculus humanus), but can be distinguished by the location where they are found.
• Head lice are found on the head. In cases of heavy infestation they may fall off onto the upper clothes.
• Pubic lice are found in pubic hair and other coarse hair, such as eyebrows, eyelashes, axillary hair, moustaches, and beards. Pubic lice can also be found around the scalp margins, particularly if the hair is widely spaced (for example in redheads, bald people, and infants).
• Body lice are found on clothes, although they feed on the body.

This information is based on expert opinion [Ibarra, 1998; PHMEG, 2008].