Head lice

Diagnosis

According to the American Academy of Pediatrics guidelines, the gold standard for diagnosing an active head-lice infestation is the identification of a live nymph or adult louse.

These guidelines recommend an examination of wet hair lubricated with such products as a standard hair conditioner. Your doctor will carefully comb your child's hair with a fine-toothed comb (nit comb) from the scalp to the end of the hair. If no live louse is found, he or she will likely repeat the entire exam at a second appointment.

Identifying nits

Your doctor will also look for nits in your child's hair. To find nits, he or she may use a specialized light called a Wood's light, which causes nits to appear bluish. But the identification of nits does not necessarily confirm the diagnosis of an active lice infestation.

A live nit needs to be near the scalp to survive. Nits found more than about 1/4 inch (6 millimeters) from the scalp are likely dead or empty. Suspect nits can be examined under a microscope to determine if they're living — evidence of a likely active lice infestation.

If no live nits are found, they're probably left from a previous infestation and do not need to be treated.

Treatment

Your doctor will likely recommend an over-the-counter (OTC) medication that kills lice and some of the nits. These medications may not kill recently laid eggs. Therefore, an appropriately timed second treatment is usually necessary to kill nymphs after they hatch but before they become adult lice.

Some studies suggest that retreating seven to nine days after the first treatment is the ideal time for a second treatment, but other retreatment schedules exist. Ask your doctor for written instructions for a recommended treatment schedule.

Over-the-counter (OTC) products

OTC medications are based on pyrethrin, a chemical compound extracted from the chrysanthemum flower that is toxic to lice. Wash your child's hair with shampoo with no conditioner before using one of these treatments. Rinsing the hair with white vinegar before washing may help dissolve the glue that holds the nits to the hair shafts. Follow directions on the package for how long to leave the medication in the hair, and rinse your child's hair over a sink with warm water.

OTC medications include the following:

• Permethrin (Nix). Permethrin is a synthetic version of pyrethrin. Permethrin does not kill nits, and treatment needs to be repeated nine to 10 days after first application. Side effects may include redness and itching of the scalp.
• Pyrethrin with additives (Rid). In this OTC medication, pyrethrin is combined with another chemical that enhances its effectiveness. This product only kills lice, not nits, and needs to be reapplied nine to 10 days after first treatment. Side effects may include itching and redness of the scalp. Pyrethrin shouldn't be used if your child is allergic to chrysanthemum or ragweed.

Prescription medications

In some geographic regions, lice have developed resistance to OTC medications. Also, OTC treatment may fail because of incorrect use, such as not repeating the treatment at an appropriate time.

If the correct use of an OTC treatment has failed, your doctor may recommend a prescription treatment. These include:

• Ivermectin (Sklice). Ivermectin is toxic to lice. It is approved for use with people age 6 months or older. It can be applied once to dry hair and then rinsed with water after 10 minutes. Ivermectin is also available as a tablet to be taken by mouth to children weighing more than 33 lbs. if other topical treatments do not effectively eliminate a lice infestation.
• Spinosad (Natroba). Spinosad is approved for use with people age 6 months or older. It can be applied to dry hair and rinsed with warm water after 10 minutes. It kills lice and nits and usually doesn't need repeated treatment.
• Malathion. Malathion is approved for use with people age 6 or older. The lotion is applied, left to dry naturally and rinsed out after eight to 12 hours. The drug has a high alcohol content, so it can't be used with a hair dryer or near an open flame. Malathion can be reapplied seven to nine days after the first treatment if necessary.

Lifestyle and home remedies

If you prefer not to use a medication for treating a head-lice infestation, you may consider an alternative home treatment. There is little to no clinical evidence of the effectiveness of such treatments.

Wet-combing

Combing wet hair with a fine-toothed nit comb may remove lice and some nits. Studies show that wet-combing results vary.

The hair should be wet, and you should add something to lubricate the hair, such as a hair conditioner or olive oil. Comb the entire head from the scalp to the end of the hair at least twice during a session. The process should be repeated every three to four days for several weeks — at least two weeks after no more lice are found.

Essential oils

Small clinical studies have suggested that some natural plant oils may kill lice by suffocation, but effectiveness is uncertain. These products include:

• Tea tree oil
• Anise oil
• Ylang-ylang oil

These products are not required to meet safety, efficacy and manufacturing standards used for drugs approved by the Food and Drug Administration (FDA), and can sometimes cause allergic reactions.

Smothering agents

A number of household products are used to treat head-lice infestations. These products are thought to deprive the lice of air when generous amounts are applied to the hair, covered with a shower cap and left on overnight. Products used for this purpose include:

• Mayonnaise
• Olive oil
• Margarine or butter
• Petroleum jelly

However, the effectiveness of these treatments is unclear.

Dehydration

Another option is a machine that uses one application of hot air in an attempt to kill head lice and their eggs through dehydration. The machine requires special training and is currently available only at professional lice treatment centers.

The machine uses air that is cooler than most hair dryers and at a much higher flow rate to kill the lice by drying them out. A regular hair dryer should not be used to accomplish this result as it's too hot and could burn the scalp.

Dangerous products to avoid

Flammable products, such as kerosene or gasoline, should never be used to kill lice or to remove nits.

Household cleaning

Lice usually don't live past one day without feeding from a human scalp, and eggs do not survive if they aren't incubated at the temperature near the scalp. Therefore, the chance of lice surviving on household items is small.

As a precaution, you may clean items that the affected person has used in the previous two days. Cleaning recommendations include the following:

• Wash items in hot water. Wash bedding, stuffed animals and clothing in hot, soapy water — at least 130 F (54.4 C) — and dry at high heat.
• Clean hair care items. Clean combs, brushes and hair accessories by soaking them in hot, soapy water for five to 10 minutes.
• Seal items in plastic bags. Seal items that can’t be washed in plastic bags for two weeks.
• Vacuum. Give the floor and upholstered furniture a good vacuuming.

Preparing for your appointment

See your family doctor or pediatrician if you suspect your child has head lice. Your doctor will examine your child's scalp and look for a live nymph or adult louse to determine if he or she has an active head-lice infestation. Your doctor can carefully inspect your child's hair and, if necessary, examine suspect items under a microscope before confirming a diagnosis of head-lice infestation.