Is it lice?

Diagnosis of lice infection is made A) by taking a patient history, B) considering lice infestation as a possible or probably cause of the patient’s signs and symptoms, C) careful examination of the patient. Both adult lice and their eggs (nits) are easily seen by the naked eye.

Head lice characetistically are found on the scalp surface with the nits attached to the hair. Since scalp hair grows at a rate of about 0.4 mm per day and nits of the head louse usually hatch within 9 days, most of the unhatched nits are within 5 mm of the scalp surface. Nits on scalp hair are usually cemented at an oblique angle, which helps to distinguish  them from foreign material that slides up and down and frequently surrounds the hair.

Upon examination of the groin or pudendal area, pubic lice may be perceived as scabs over what first were thought to be “Scratch papules.” When taking a closer look, if nits appear on the hairs, proper diagnosis becomes obvious. When no adult lice are available, the demonstration of nits under the microscope will also confirm the diagnosis.

When one sees with the naked eye white flakes on the hair, other possible considerations are seborrheic dermatitis (dandruff flakes), hair casts, solidified globules of hair spray, and certain accretions on hair shafts.

With this image below one can observe what the louse or lice looks like with the naked eye. In this imaged condition the crab has infected the area of the eye, a condition called phthiriasis palpebrarum or pediculosis ciliaris. Point A) is a nit, Point B) is an actual louse, notice it has six legs and point C) is a nit.

Nits and louse on an eyelash

Point B is an actual louse and it is pretty big in size. Compare it to the picture below of louse magnified.

magnified crab louse


(Back to background and history of pubic lice from “Is it lice”)