Head lice are a common concern, primarily affecting children. These tiny insects feed on human blood and can cause discomfort and itching. A more challenging variety, known as “super lice,” has emerged, raising questions about effective treatment.
Head Lice Basics
Head lice, scientifically known as Pediculus humanus capitis, are small, wingless insects that live on the human scalp. An adult louse is about the size of a sesame seed and typically grayish-white or tan. They move by crawling and cannot jump or fly, spreading primarily through direct head-to-head contact.
The life cycle of a head louse involves three stages: nit, nymph, and adult. Nits are lice eggs, often appearing as tiny yellow or white specks firmly attached to the hair shaft near the scalp. After about 7 to 10 days, nits hatch into immature lice called nymphs. Nymphs mature into adult lice in about 7 days. An adult louse can live for up to 30 days on a person’s head, laying several nits per day.
The Rise of Resistant Lice
The term “super lice” refers to head lice that have developed genetic resistance to common over-the-counter (OTC) pesticide-based treatments. These treatments traditionally contain pyrethrins or permethrin, which are neurotoxins that paralyze and kill lice. The widespread and often repeated use of these insecticides has exerted selective pressure on louse populations.
This resistance is primarily linked to specific genetic mutations, often referred to as “knockdown resistance” (kdr) mutations. These mutations alter the lice’s nervous system, making them less susceptible to pesticides. Visually, resistant lice appear identical to non-resistant lice; the distinction is their genetic makeup and response to chemical treatments.
Recognizing an Infestation
Identifying a head lice infestation involves checking for specific signs, regardless of whether the lice are resistant or not. The most common symptom is itching on the scalp, neck, and ears, caused by an allergic reaction to louse saliva. This itching may not begin immediately, sometimes taking several weeks to develop.
Visible nits are another clear indicator. They are typically found firmly glued to individual hair strands, close to the scalp, and cannot be easily brushed or flicked away. Live, crawling lice may also be seen, though they are often fast-moving and difficult to spot. A thorough check involves parting the hair section by section under good lighting and using a fine-toothed lice comb.
Effective Treatment Strategies
Treating head lice, especially if resistance is suspected, requires specific approaches. For infestations where traditional treatments might still be effective, OTC pediculicides containing permethrin or pyrethrins can be considered, though their efficacy has declined in many regions. Careful adherence to product instructions, including follow-up treatments, is important.
When dealing with “super lice” or in cases where initial treatments fail, alternative strategies are necessary. Non-pesticide options, such as products containing dimethicone or benzyl alcohol, offer different mechanisms of action. Dimethicone suffocates lice by coating them, while benzyl alcohol works by paralyzing the lice’s respiratory spiracles, leading to suffocation. Manual wet-combing with a fine-toothed comb is also a highly effective method, physically removing lice and nits. Prescription medications are available through a healthcare provider if other treatments are unsuccessful.