Head lice are parasitic insects that live on the human scalp and hair. Although these pests are small, they are visible to the naked eye, allowing for self-diagnosis. Understanding their appearance at each life stage—adult, nymph, and egg—is necessary to distinguish them from common hair debris. This guide provides the specific details needed to identify an active head lice infestation.
Identifying Adult Lice and Nymphs
Adult head lice are tiny, six-legged insects, roughly the size of a sesame seed (two to three millimeters long). Their color is typically grayish-white or tan, but they may appear darker or rust-colored after feeding on blood from the scalp. They are wingless and cannot jump or fly, instead using specialized claws to crawl quickly along the hair shaft. This speed and their ability to avoid light often make them difficult to spot.
The juvenile stage, known as a nymph, looks like a smaller version of the adult louse. Nymphs are generally the size of a pinhead and are lighter in color when they first hatch. They mature into adults approximately nine to twelve days after emerging from the egg. Finding a live, crawling louse or nymph confirms an active infestation.
Distinguishing Nits (Eggs) from Other Flakes
Lice eggs, commonly called nits, are the most frequently seen visual evidence of an infestation. Nits are tiny, oval-shaped objects, less than one millimeter long, that are firmly cemented to the hair shaft. A female louse secures each egg with a waterproof, glue-like substance. This firm attachment ensures the nit cannot be easily washed or brushed away, which separates them from other particles.
Viable nits are usually found within a half-inch of the scalp, where the temperature is warm for incubation. Their color is typically yellowish-white or tan, and they may possess a slight sheen. Look-alikes, such as dandruff or dried skin flakes, are irregularly shaped and lack this firm attachment, moving freely when brushed. Hatched nits appear clearer, duller, or more translucent and are found farther down the hair shaft as the hair grows out.
Contextual Signs of an Infestation
While live lice and nits are the direct signs, their presence is often concentrated in specific areas of the head. Lice and nits prefer the warmer, more protected regions of the scalp. These “hotspots” are most notably the nape of the neck and the area directly behind the ears. Examining these areas with a bright light increases the chances of detection.
Secondary visual cues may also confirm an infestation, often resulting from the host’s reaction to the parasites. Small red bumps or scratch marks on the scalp, neck, and shoulders can appear due to the allergic reaction from louse bites and subsequent scratching. An intense, persistent itching or a distinct tickling sensation may also be reported, especially at night when the lice are more active. Occasionally, tiny dark specks, which are louse excrement or shed skin, may be visible on the scalp or pillow.