Although all members of the family need to be inspected for head lice, an insecticidal treatment for the hair should be applied only to individuals that have been confirmed as having head lice. Do not use an insecticidal strategy unless head lice have been detected.
The most common way to approach head-lice control has been to use a chemical treatment, called a pediculicide. Such treatments come in various forms: shampoo, cream rinse, gel, mousse, and oil spray. These products can be quite expensive. Even though most of these products are available without a prescription, they contain an insecticide and should be given the same respect as a prescription drug.
Read the label to determine the active ingredient(s). Over-the-counter products that list permethrin (i.e., Nix®) or pyrethrins (also known as pyrethrum extract) contain insecticide(s). Pyrethrins often are combined with piperonyl butoxide, a synergist that increases their activity against head lice; some examples include LICEX®, RID®, Pronto®, R&C® Lice Treatment, Clear® Lice Killing Shampoo, etc. Ovide® is a prescription-only product that contains the insecticide malathion.
Lindane (Kwell®) is a potent insecticide that is available only by prescription and only as a second-line treatment for people who cannot tolerate other chemical therapies or where other products have failed. However, be aware that lindane is readily absorbed through human skin, has a long half-life, and is relatively toxic to mammals. Use of lindane has been associated with convulsions and seizures in humans. Because of human health concerns, lindane is seldom recommended for head-lice control; there are many less toxic alternatives for head-lice control.
Resistance to the insecticides found in head-lice products is a potential cause of treatment failures. Resistance of head lice toward lindane has been documented over the years.
Several recent clinical studies also indicate that head-lice populations have developed varying levels of resistance to permethrin and malathion. Resistance currently seems to be less of a problem with pyrethrin/piperonyl butoxide combinations. However, be aware that lice can eventually develop resistance toward most, perhaps all, insecticides.
Do not keep using the same product over and over again. If one product is not working, try another approach or use a product that contains a different active ingredient. Consult your physician if you have difficulty getting rid of the head-lice infestation.
When using any insecticidal treatment, read and closely follow all instructions. Be aware that over-treatment can be toxic to humans. If the treatment is to be reapplied after 7–10 days, do so since head-lice eggs may have hatched within this period. Do not apply the product any more or less often than is recommended on the label. Consult your physician or pharmacist if you have questions or need additional information.
Take a number of precautions prior to using an insecticidal head-lice product. Contact your physician for medical advice if the person applying the treatment or receiving the treatment is pregnant or has asthma, allergies, or any other medical condition. Also, seek advice from your physician if the pediculicide will contact any open cuts in the skin, such as those caused by scratching.
Use disposable rubber gloves when applying an insecticidal product. Take care to treat only the head, not the rest of the body of the affected person. Keep the pediculicide out of the eyes, nose, mouth, and any mucus membranes. The affected individual should either sit, leaning head back, or they should lie on a cushioned counter with the hair draped into a sink or other receptacle. They should be in a comfortable position to help avoid squirming. (Do not apply to the affected person's head while they are in the tub. Do not have them lean their head forward, because of the increased possibility of inhaling fumes or having the chemical contact the face.) Apply the insecticidal product to a cool head. Warmth opens up the pores in the skin and an excessive amount of the chemicals can be absorbed.
Even after taking these precautions, if the chemical solution gets in the eyes, rinse quickly and gently with lukewarm water or normal saline solution (used for rinsing contact lenses) for 10–15 minutes or more. Apply a cool, wet cloth over the closed eyes and have the individual rest. Contact your physician if visual changes occur or burning persists.