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Head Lice Life Cycle

The Life Cycle of Head Lice, and Their Symptoms and Treatment

Head lice infestations occur more often in children than in adults, with around 6 - 12 million cases in the US every year. Understanding the life cycle of these tiny creatures can help in dealing with this infestation in a better way.
Marian K
Last Updated: Apr 22, 2018
Head lice are tiny little insects that take up residence on a person's head. While they aren't dangerous and do not play a role in the spread of any disease, their presence is socially embarrassing and can affect a person psychologically.
Life Cycle of Head Lice
The life of head lice progresses in three stages: nit, nymph, and adult. Like many other forms of life, the first stage of existence of a head louse is as an egg, called a nit. An adult female lays the egg at the base of a strand of hair, where it remains attached by an adhesive substance. The eggs are laid with proximity to the scalp, as the heat it generates is needed for incubation. The nits are approximately 0.8mm by 0.3mm in dimension, oval in shape and possess a color between white and yellow. On an average, they hatch 6 to 9 days after being laid.
The next stage in its life cycle is when the egg hatches and out comes the nymph. It shares the appearance of a grown louse, but is only smaller in size. Nymphs are usually as small as a pinhead and have a yellow to rust-color. The shell it emerges from turns yellow while remaining attached to the strand of hair. As the nymph grows, it sheds its exoskeleton 3 times before attaining adulthood. The nymphs wander at the neckline and behind the ears while remaining closer to the scalp. They enter adulthood in about 7 days time.
The adult stage is marked with a 5 times a day feeding pattern. It does this by penetrating the skin using its claws and sucking out blood. Without these regular meals, an adult louse dies within a day or two. Post feeding, the lice take on a rust color, though, otherwise they appear grayish-white. Adult lice are usually the size of a sesame seed, with females being larger. They have 6 legs with sharp claws used to maintain a firm grip on the strands of hair. Nestled safely on a person's head, they can live for up to 30 days. During this time, the females can and may lay up to 8 nits per day.
Symptoms and Treatment
The first and foremost sign of head lice infestation is itching. Upon checking, one can spot these tiny insects moving about in a person's hair. They can also cause the lymph nodes, in the back and front of the neck to swell. People usually contract head lice from a person, who already has an infestation. This may happen due to direct contact with the hair or head of that person or even by using their combs/brushes, scarves hats, or coats. However, they can also spread through pillows, towels, beds, and stuffed toys.
There are several medications for head lice treatment. Pediculicides, is one of the most effective medications and they have to be applied directly to the scalp and hair, and rinsed after 10 minutes for better result. These medications effectively kill nymphs and adult lice, but fail to destroy nits. However, the nits can be dealt with by applying a second round of the medication after 7 to 10 days, by which time, they would have hatched. Nits can also be removed using a fine toothed comb.
Understanding about the life cycle of head lice puts one in a better position to treat an infestation. If one child or family member has a case of head lice, all other members must also be checked for lice.