Tests and diagnosis

By Mayo Clinic Staff

During an examination, your doctor may examine you for lice using a magnifying lens and check for nits using a special light, called a Wood's light, which makes the nits look pale blue.

Head lice

A diagnosis of head lice can be made after a live young or adult louse in the hair or on the scalp is found, or after one or more nits is seen on hair shafts located within 1/4 inch (6.4 millimeters) of the scalp.

If you don't see any live lice or you see nits that are more than 1/4 inch away from the scalp, the infestation is no longer active and you don't need treatment.

Body lice

A diagnosis of body lice may be made if eggs or crawling lice are found in the seams of clothing or on bedding. It's possible to see a body louse on skin if it crawls there to feed.

Pubic lice

Pubic lice are diagnosed when moving lice or nits are seen on hair in the pubic area or on other areas of coarse hair, such as chest hair, eyebrows or eyelashes.

May. 22, 2012