The Life Cycle of Head Lice

Head lice are parasitic insects that like to live in the hair and on the heads of humans. Although the presence of head lice can be somewhat disturbing they present no real health hazard and they have not been found to carry or spread any diseases. Head lice are more commonly found on children than adults and for unknown reasons they are rarely found on the heads of African Americans. Some speculate that hair strand width and shape are the reasons for this.

General Facts

• The medical name for head lice infestation is Pediculus Humanus Capitis and they feed by biting and scraping the scalp to get at the blood underneath. If left untreated they can continue to reproduce at an alarmingly fast rate. The life span of a single louse from egg to adult is about one month, although without a head to live on they can only survive for about two days.

Head Lice in the Family

• Most families with children usually experience head lice at some time or another. There are 6 to 12 million cases of head lice infestation reported each year and the majority of them are children. This is because children tend to play in close contact with each other, often sharing hats, clothing, beds and brushes. Although fairly easy to treat a child can easily catch head lice again if they come in contact with another infested child.

Nit Stage

• Head lice have three stages to their life cycle: nit, nymph and adult. Nits are the egg stage of the head lice and are found attached to the base of a hair strand. Using the heat from the head to incubate them, the nits usually hatch 6 to 9 days after being laid. They tend to be oval in shape and are a white to light yellow in color. A single female louse can lay up to 150 eggs within a month.

Nymph Stage

• Nymphs look very similar to the adult louse except that they are slightly smaller and do not yet posses reproductive organs. A nymph will shed its skin three times before it reaches the adult stage, which takes about seven days from nit to adult. Although nymphs are in a constant state of growth their size can vary, but generally they are the size of a pin head.

Adult Stage

• Adult lice are usually gray in appearance but after they feed their color can change to a rust color. The female louse is usually larger than the male and lives for 9 to 22 days, whereas the lifespan of the male is about 10 days. The adult head lice feed about five times a day by scraping and biting at the scalp and drinking the blood. While feeding they attach themselves to the hair with hooks on the ends of their legs. They can be hard to dislodge like ticks but a dousing with baby oil or a lice shampoo is normally enough to loosen them enough to be combed out with a lice comb.