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How to tell if you have crab lice

Itching occurs, especially at night, in the pubic hair area.

Seeing the lice. The lice are small (up to 2 mm long), and can just be seen with the naked eye. They are squat in shape and, with a magnifier, you can see that all the legs emerge close together from the front of the body, and the middle and hind legs have large pincer-like claws giving the ‘crab’ appearance. They use their claws to grasp hairs close to the skin surface. They hardly move except at night, when they slowly transfer their grip from one hair to another.

Nits, which are the egg cases, can be seen attached to the hairs. The female lays the eggs in a hard brown shell, which she attaches to the hair on the surface of the skin. As the hair grows, the egg case will be further up its shaft, so the position of the nits on the hair gives you an idea of how long you have had them. After about 8 days the eggs hatch, and the empty egg case appears white and is easier to see.

Rust-coloured specks may be seen on the skin – these are louse faeces.

Blood specks may be seen on underwear.

Written by: Dr Margaret Stearn
Edited by: Dr Margaret Stearn
Last updated: Saturday, February 13th 2010

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Comments on this article

Posted by Anonymous on 02/11/2009 at 11:33:00 am

CAN CRAB LICE SECRETE THEMSELVES ON A HOST'S BODY OTHER THAN IN HAIRY LOCATIONS - CAN THEY LIVE IN THE ANNAL PASSAGE?

Posted by Anonymous on 29/05/2009 at 04:29:00 am

My parent says that I don't have crabs because of my young age but i've shown practicaly all of the symptoms and I was scratching my pubic area and found something the size of a small ball of lint I opened my fingers and all I saw was something black (I think) as it was in mid jump from my fingers and then couldn't find it on the floor. Should I be worried?