(HealthDayNews) -- Head lice are parasitic insects, and anyone who comes in close contact with someone who has head lice or contaminated clothing can acquire them.

Most often, it's preschool and elementary-age children and their families who become infested, according to U.S. Centers for Disease Control and Prevention.

There are three forms of lice: the nit, the nymph and the adult. Nits are eggs and are found attached to the hair shaft. The nit hatches into a baby louse called a nymph. The adult louse is about the size of a sesame seed, has six legs and is tan to grayish-white. Adult lice feed on blood.

Signs of head lice infestation include a tickling feeling, itching and sores on the head from scratching.

If head lice are found, treat the infested person with an over-the-counter or prescription medication. Before applying treatment, remove all clothing. Have the infested person put on clean clothing after treatment. Comb dead and remaining live lice out of the hair.

Nit combs, often found in lice medicine packages, should be used to comb nits and lice from the hair shaft.

Head lice do not survive long if they fall off a person. But you need to machine-wash clothing and bed linens that the infested person touched during the two days before treatment. Use hot water. Dry laundry using high heat for at least 20 minutes. Dry clean clothing that is not washable.

Soak combs and brushes for an hour in rubbing alcohol, Lysol or wash with soap and hot water. Vacuum the floor and furniture.