Head Lice

These are two words no parent wants to hear. Head lice infections are common and each year between 6 and 12 million US children between the ages of 3 and 11 years are infested with head lice. Household members of these preschool and school aged children are also at risk for infestation.
The biggest concern with head live is discomfort due to itching and secondary bacterial skin infections and further spread of the infestation to others. Lice do not transmit disease but the effects on the family in terms of days lost at school and parents being unable to go to work due to child care responsibilities are substantial.
Although hygiene and hair length are not the cause of head lice infection, an infestation often causes many families to be embarrassed and suffer social stress and isolation.
The rash that is seen with a head lice infestation is due to the body developing sensitivity to the saliva of the louse which is injected under the skin when it is feeding on the host. It may take up to several weeks for the sensitivity and subsequent itching to develop.
A louse is about the size of a sesame seed and has six legs. The louse can live for up to a month and lays up to 10 eggs per day. The eggs are attached to the base of a hair shaft. Eggs that are not at the base of the hair shaft are not viable. When the eggs hatch the casings (nits) are white and easier to see. Within 10 days after hatching a louse can begin to lay eggs and the cycle continues. Eggs cannot hatch at room temperature. Body heat is needed to incubate.
Lice will die if not on a host for 24 hours. They do not jump or fly. They crawl quickly and sometimes can be seen easier if you use a lubricant such as oil, hair conditioner or water to slow them down. They avoid light.
It is best only to treat children who have living lice. Over half of all children with nits do not have living lice. Prevention is difficult and depends on avoiding head to head contact. Children need to avoid the sharing of combs, brushes and hats. Prompt treatment of children with living lice is the best way to curtail an outbreak.
Various medications are available for treatment. Choice depends on patient age and medication availability as well as potential side effects. Lice have become resistant to certain medications and often another medication may need to be used if the first medication fails to eradicate the infestation.
Treatment includes OTC medication containing 1% permethrin (Nix). The hair should be shampooed with a non-conditioning shampoo and then towel dried. The medication is applied thoroughly to damp hair and left on for 10 minutes. It is then rinsed off with warm water and the process is repeated in 7-10 days if live lice are seen. Nix is the least toxic lice medication and rarely causes redness, itching or scalp swelling. Permethrin (Nix) does leave a residue on hair that kills newly hatched lice for several days. The use of hair conditioners and hair products with silicone based additives hinders this protection and should be avoided for several days.
Another commonly used medication is malathion (Ovide). It is available by prescription. It is applied to the hair and scalp while eyes are tightly shut. The hair should start dry and end thoroughly wet. Leave hair air dry and uncovered. Shampoo hair after 8-12 hours and use nit comb to remove lice and eggs. It appears to be more effective than Nix but has more side effects. It has not been studied in children under age 6 years and is not used in children under age 2 years. It is highly flammable and contains almost 80% isopropyl alcohol. Avoid high temperatures and open flames while the hair is wet.
Another medication is benzyl alcohol (Ulesfia). It is available by prescription. It is applied to hair to completely saturate scalp and hair. Short hair takes 4 ounces and long hair up to 24 to 48 ounces. Rinse off with water after 10 minutes and repeat in 9 days. It kills lice by suffocating them. It is approved for children over age 6 months and can cause eye and skin irritation. In children under 6 months it can cause severe metabolic disturbances due to skin absorption.
Spinosad (Natroba) was approved by the FDA in 2011. It is used in children 4 years  and  older. It is applied to dry scalp and hair to cover the entire area. Apply up to 120 ml depending on hair length and leave on for 10 minutes. It is then thoroughly rinsed off with warm water and repeated in 1 week if live lice are seen. It is derived from the fermentation of a soil bacterium and may be more effective than Nix. It can cause application site irritation due to benzyl alcohol in the product.
The most recent new product is ivermectin (Stromectol). It comes in a 0.5% lotion called SKLICETM) and is indicated for head lice treatment in patients 6 months and older. It is applied to dry hair to cover scalp and hair and left on for 10 minutes and then rinsed off with warm water. A nit comb is not necessary. The person who applies the medication should wash their hands thoroughly after application. Repeat treatment is not needed.
Lindane (Kwell) is no longer indicated for the treatment of head lice. It can cause serious neurotoxicity and seizures.
Occlusive agents like mayonnaise, margarine and various oils have been used with varying effects in an attempt to suffocate head lice. Head shaving is effective but is undesireable for cosmetic reasons. Frequent wet combing with a nit comb and shampoo or conditioner as a lubricant may also be effective.