Head lice infestation, medically known as pediculosis, is a common issue primarily affecting school-aged children and their close contacts. The parasitic insects lay their eggs, called nits, firmly onto the hair shafts. Nits are often the first sign of an infestation, causing considerable confusion and anxiety for those attempting treatment. Understanding the physical makeup of these eggs is the first step in effective treatment and dispelling common misconceptions.
The Physical Nature of Nits
The question of whether lice eggs “pop” often comes from crushing them between fingernails or the teeth of a comb. Nits do not burst like a fluid-filled sac; instead, they produce a slight snapping sound when compressed. This audible noise is the hard, chitinous shell of the egg fracturing under pressure, not internal fluid escaping. The structure of the nit is a rigid, oval casing designed to protect the developing louse inside.
A female louse attaches each egg to an individual hair strand using a powerful, cement-like bio-adhesive that is incredibly resistant to washing, shampooing, and normal hair care products. This glue ensures the nit remains fixed on the hair shaft for the entire 6-to-9-day incubation period until it hatches. Because of this strong bond, the only way to remove a viable nit is to physically scrape the shell off the hair shaft.
Distinguishing Nits from Common Look-alikes
Identifying a true nit requires distinguishing it from common hair debris, often referred to as pseudo-nits, such as dandruff, product residue, or hair casts. The primary differentiating factor is the nit’s attachment: a true nit is teardrop or oval-shaped and is tightly cemented to one side of the hair shaft. Unlike dandruff flakes or dry skin, which move or slide off the hair easily with a light touch, a nit will remain firmly in place.
Viable nits are typically dark brown, tan, or yellowish, blending in with the hair color. They are found within six millimeters of the scalp where the temperature is optimal for incubation. Once the louse hatches, the empty shell remains glued to the hair, appearing white or translucent. A hair cast is a tubular sheath of keratin that completely encircles the hair shaft but, like dandruff, can be easily slipped off the hair. If the particle slides easily, it is not a nit.
The Nit Life Cycle and Effective Removal
The lice life cycle begins when a female louse lays her eggs, typically producing up to eight nits per day, which she glues close to the scalp. After an incubation period of six to nine days, the nit hatches into a nymph, an immature louse. Nymphs require about ten days and three molts to reach the adult stage, at which point they begin reproducing, continuing the cycle. The full life cycle from egg to adult is approximately 19 days.
Effective removal must address both adult lice and cemented nits to break this reproductive cycle. Since the nit’s glue is water-insoluble, treatment often involves specialized products or acidic rinses designed to weaken the bond. The most reliable method for nit removal is systematic wet-combing using a fine-toothed metal nit comb. This process involves coating the hair with conditioner, which immobilizes the live lice, and then physically scraping the hard, glued shells from the hair shaft.
Because most chemical treatments do not kill all nits, retreatment is recommended seven to ten days after the initial session. This second treatment targets newly hatched nymphs before they mature into egg-laying adults, ensuring the complete elimination of the infestation. The physical removal of the hard-shelled eggs is necessary to clear the hair and confirm the treatment has been successful.