Head lice are tiny insects that live on the human scalp, feeding on small amounts of blood. They are a common problem, particularly among children, and spread easily through close contact. A common misconception is that chlorine, like that found in swimming pools, can eliminate lice.
Chlorine’s Limited Impact on Lice
Chlorine, even at concentrations found in swimming pools, does not effectively kill head lice or their eggs, known as nits. While submerging lice in chlorinated water may temporarily stun them, they typically recover quickly once removed. Studies show lice submerged for 20 minutes can fully recover in less than a minute.
Lice possess adaptations allowing them to survive in aquatic environments. Their protective outer layer, or exoskeleton, helps them resist mild chemicals and shed water. Lice can also hold their breath for extended periods by closing their spiracles, their breathing holes. This ability allows them to survive underwater for several hours, with some sources indicating up to 8 hours. Nits are even more resilient; they are firmly glued to the hair shaft with a water-insoluble adhesive that chlorine cannot dissolve.
Effective Lice Treatment Approaches
Since chlorine is not an effective solution, addressing a lice infestation requires targeted approaches.
Over-the-Counter (OTC) Treatments
OTC treatments are a common first step, often containing active ingredients like pyrethrins or permethrin. Pyrethrins, derived from chrysanthemum flowers, kill live lice but do not typically kill unhatched eggs, necessitating a second treatment 9 to 10 days later. Permethrin, a synthetic pyrethroid, also targets live lice and may kill newly hatched lice for several days, often requiring a repeat application around day nine. Always follow product instructions carefully, as resistance to these ingredients has been observed.
Prescription Medications
For cases where OTC treatments are ineffective or resistance is suspected, prescription medications are available. These include topical solutions like benzyl alcohol lotion, ivermectin lotion, malathion, and spinosad. Spinosad kills both live lice and unhatched eggs, often eliminating the need for retreatment or nit combing. Oral ivermectin is another prescription option for children weighing over 33 pounds if topical treatments fail.
Manual Removal (Wet Combing)
Manual removal, or wet combing, is a widely recommended non-chemical method that can be used alone or with medicated treatments. This process involves applying ample conditioner to wet hair and then systematically combing through small sections from the scalp to the ends using a fine-toothed nit comb. The conditioner helps slow down lice and makes removal easier. Regular wet combing every 2 to 3 days for several weeks helps break the lice life cycle by physically removing both lice and nits.
Environmental Cleaning
Environmental cleaning supports lice management, though it is less central than treating the infested individual. Lice cannot survive long off a human host, typically less than 24 to 48 hours. It is advisable to clean items recently used by the infested person:
- Machine wash and dry clothing, bedding, and other items in hot water (at least 130°F) and high heat.
- Seal items that cannot be washed in a plastic bag for two weeks.
- Soak combs and brushes in hot water for 5 to 10 minutes.
- Vacuum floors and furniture to remove any stray lice or hairs with nits.
Lice and Aquatic Environments
The risk of head lice transmission in swimming pools is low. Lice do not swim and primarily spread through direct head-to-head contact. When submerged, lice cling tightly to the hair and do not readily leave their host. Research indicates that even if a person with lice swims in a chlorinated pool, the lice are unlikely to spread to other swimmers through the water itself.
While the water itself poses minimal risk, sharing personal items associated with swimming can contribute to spread. This includes towels, swim caps, combs, and hairbrushes. To minimize any potential for spread, it is advisable to avoid sharing such items. Some lice treatments can also be affected by chlorine, so it is generally recommended to avoid swimming or washing hair for 24 to 48 hours after applying certain lice medications.