Lice

Itching, the most common symptom of all types of lice infestation, is caused by an Reference allergic reaction Opens New Window. Lice bite the skin to feed on a person's blood. The saliva from these bites causes the allergic reaction and itching.

Itching may not occur right away, depending on a person's sensitivity and history of lice infestation. The first time a person is infested with lice, it may take several weeks or months for itching to start or to be noticed. In a repeat case of lice, a person may begin to itch within 2 days of infestation because the Reference immune system Opens New Window reacts more quickly when exposure has occurred before.

Some people become very sensitive to lice bites and have unbearable itching. Others build up tolerance to the bites and have little or no itching, even with repeated infestations.

In addition to itching, symptoms of lice infestation vary depending on which type of lice is present.

Head lice

Reference Head lice Opens New Window Reference Opens New Window and their eggs (nits) can be Reference seen on hair Opens New Window Reference Opens New Window, the nape of the neck, and behind the ears. They can vary in color from white to brown to dark gray. The eggs are tiny round or oval shapes that are tightly attached to the hair near the scalp and do not slide up and down on the hair.

Frequent scratching may cause broken skin or sores to form on the scalp. The damaged skin may weep clear fluid or crust over, and it may become infected. In response to infection, the lymph nodes behind the ears and in the neck may become tender and swollen.

Pubic lice

A Reference pubic lice Opens New Window Reference Opens New Window infestation may cause itching around the genitals as well as the anus, armpits, eyelashes, and other body areas with hair. Pubic lice bites may cause small, flat, blue-gray marks (maculae cerulea) that look like bruises on the torso, thighs, or upper arms. The marks may last for several months, even after all lice have been killed. Pubic lice, like head lice, can be seen on shafts of hair.

Pubic lice that infest the eyelashes and eyelids may cause irritation and crusting in those areas. The lice may be visible near the base of eyelashes.

Pubic lice tends to be spread by sexual contact. If you or your teen has pubic lice, you may also have some other sexually transmitted infection (STI). Reference Symptoms of STIs Opens New Window can include itching, tingling, burning, or pain of the genitals. For more information about STIs, see the topic Reference Exposure to Sexually Transmitted Infections.

Body lice

Itchy sores from Reference body lice Opens New Window Reference Opens New Window usually develop in the armpits, around the waist, and along the trunk where seams of clothes press against the skin. The lice and eggs are generally not seen on the skin but may be found in the seams of the person's clothing.

Other conditions, such as dandruff or Reference scabies Opens New Window, can cause symptoms similar to those of a lice infestation.

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