The term “nits” refers to the small eggs of the head louse, Pediculus humanus capitis. These minute eggs are firmly attached to the hair shaft by the adult female louse, making them difficult to remove and signaling the start of a head lice infestation.
The Life Cycle of Head Lice
The head louse progresses through three stages: the nit (egg), the nymph, and the adult louse. The life cycle begins when a female louse lays an oval-shaped nit, gluing it close to the scalp, typically within 6 millimeters of the skin, where the temperature is optimal for incubation. Nits require body heat and generally hatch within six to nine days.
Once hatched, the immature louse, called a nymph, emerges, leaving behind the empty, white or translucent eggshell still firmly glued to the hair. A nymph requires about seven days to mature into an adult louse. The fully grown adult louse is roughly the size of a sesame seed and is tan to grayish-white. Female adult lice can lay up to eight eggs daily, continuing the cycle for their lifespan of up to 30 days on a human host.
Identifying Nits vs. Common Debris
Identifying nits relies on distinguishing them from common look-alikes such as dandruff or hair spray droplets. A primary characteristic of a nit is its firm attachment to the hair shaft, secured by a waterproof, glue-like substance. Unlike dandruff, which flakes off easily, a nit remains fixed in place.
Before hatching, nits are small and oval-shaped, appearing yellowish, white, or tan. After a nymph emerges, the empty shell remains as a dull white casing. Nits are almost always found very close to the scalp, particularly behind the ears and near the nape of the neck, where warmth is greatest. If the particle slides easily along the hair strand, it is not a nit. The presence of firmly attached nits is a strong indicator of a current or recent infestation.
Comprehensive Removal and Treatment Options
Eliminating nits and lice often combines mechanical removal with medicated treatments. The primary mechanical method is wet-combing, which utilizes a fine-toothed nit comb on wet hair coated in a thick conditioner. The conditioner temporarily immobilizes the adult lice and nymphs, making them easier to trap and remove. Wet-combing is a non-toxic method effective against both lice and nits.
For effective removal, the hair should be divided into small sections. The comb must be drawn firmly from the scalp to the end of the hair, wiping the comb clean after every stroke. This process should be repeated every few days for at least two to three weeks to ensure all newly hatched nymphs are removed before they can reproduce.
Over-the-counter (OTC) treatments containing insecticides like permethrin or pyrethrins can be used to kill live lice. These treatments are applied to dry hair and must be followed exactly according to package directions. Since many chemical products do not effectively kill all nits, a second treatment is needed seven to ten days later to kill any newly hatched nymphs. For suspected resistance to common OTC treatments, a healthcare professional can recommend prescription options, such as lotions containing ivermectin or spinosad.
Preventing Future Infestations
Preventing the spread of head lice involves personal strategies and environmental cleaning. Since transmission primarily occurs through direct head-to-head contact, avoiding hair-to-hair contact during play or group activities is the most effective personal measure. Teaching children to maintain personal space can significantly reduce the risk of transfer.
Discourage the sharing of personal items that touch the head:
- Hats.
- Scarves.
- Coats.
- Hair accessories.
- Combs.
- Brushes.
Combs and brushes used by an infested person should be disinfected by soaking them in hot water (at least 130°F) for five to ten minutes. Although lice are unlikely to survive long off the scalp, machine wash and dry clothing, bedding, and towels used in the two days prior to treatment. Washing these items using the hot water cycle and drying them on high heat will kill any stray lice or nits. Non-washable items like stuffed animals or headphones can be sealed in a plastic bag for two weeks to eliminate the parasites. Regular screening with a nit comb, especially after exposure, helps detect new cases early.