Life Cycle of Head Lice

Head lice are a common problem experienced by many children every year. They are easy to transmit and can be difficult to get rid of. Elementary age children seem to be particularly susceptible to head lice infestation, because they usually are not as careful about not sharing hair brushes, combs, or clips and hair items. However, anyone can get head lice.

Head lice begin their lives as tiny yellowish white eggs called nits. These nits are attached to the hair strand at an angle near the scalp. This serves to give them the warmth they require to incubate and hatch, and also makes them difficult to remove. The nits are attached to the hair strands by a very strong bond, almost like glue. Nits must be laid by live lice-it is not possible to 'catch nits' from sharing brushes and combs.

The nits hatch after seven to ten days of incubation. The newly hatched lice are clear right after they hatch. This makes them almost impossible to see on examination. They quickly develop a reddish brown coloration as they feed and grow. This coloration is created by the iron in human hemoglobin that they feed on. Head lice feed exclusively on human blood and cannot live on pets or inanimate objects. Their bites on the scalp cause localized irritation and severe itching.

The head lice go through several life stages as they grow to adulthood. The newly hatched louse is known as a 1st nymph. They progress through a 2nd nymph and 3rd nymph stage before reaching their adult size and form. This takes only seven to ten more days, and then the female head lice are mature enough to begin laying their own nits. A fully grown adult head louse is about the size and shape of a sesame seed and has six legs with clawed feet to hang on to the hair strands.

Head lice are crawling insects. They cannot jump or fly. However, they are still highly contagious. Contrary to popular belief, head lice can be transmitted from swimming pools, ponds, and lakes when people swim together in groups. When submerged in water, live head lice enter a kind of 'suspended animation' but do not die. (This is how they survive bathing and shampooing the hair without being killed.) If they float away from the infected person's head and come into contact with another person's hair, they automatically grasp the hair strand. This transmits the head lice to that other person.

An adult head louse can live for approximately thirty days on a host. During this time, a female head louse can lay one hundred or more nits. Male head lice are somewhat smaller than female head lice but live for approximately the same amount of time. Although it is rare, head lice have been known to transmit disease with their bites. Documented cases have shown that head lice can transmit typhus and recurring fevers. Luckily, head lice usually starve and die within twenty four hours of separation from a host.