How Long Can Head Lice Live?
Head lice create a universal health problem, particularly for children. Like every parasite, the house needs a host in order to survive. For head lice, this host is a human head. They suck blood from the scalp, their only supply of nourishment. Generally, lice live close to the scalp, but can sometimes breed on eyelashes and eyebrows too.
People infested with head lice scratch their head relentlessly because the lice bites actually cause an allergic reaction to the louse’s saliva, secreted as they feed on your blood.
How long do lice live? What does their life cycle look like? Keep reading for more information:
LIFE CYCLE OF A LOUSE
Head lice have 3 life stages. They begin as eggs, known as “nits.” Once a louse lays a new egg, its life cycle begins with the nit stage. A 1mm whitish-yellow fleck, the nit glues itself to a single hair strand close to the scalp. After a period of seven to ten days, the nit hatches out of its shell and becomes a nymph (young louse). And so begins stage two. Typically between 1.1 and 1.3 mm in size, nymphs appear coffee-colored or white. Within 9 to 7 days, nymphs grow into adult lice. Their 3 larval stages occur in this period of time. Nymphs molt into their next larval stage after a blood meal. Lice go through what is termed a “gradual metamorphosis.” This means that they pass to their adult stage without experiencing a non-feeding pupal stage. Once a nymph develops into an adult louse, it feeds on blood every 4-8 hours. Though, as we’ll expand upon later, they can survive for a day or two without feeding. Mature lice won’t exceed 2mm in size, and female lice grow larger than males.
The Louse Life Span with a Human Host
As soon as nits hatch, they need blood to survive. By making use of their claws to crawl from one hair shaft to another, lice feed on the host’s blood several times throughout the day. With an available source of nourishment, an adult louse can survive up to 30 days on the human head. They keep the infestation going by laying new nits, so they reproduce quickly and constantly. Female lice lay as many as 10 eggs each day. Nits can die while still on their host. As a rule of thumb, if a nit is half an inch or more from the scalp, then it may be dead. This is especially probable if no live lice accompany the found nits. Considering how many eggs lice lay, however, an infestation likely won’t dye out without intervention. In fact, an infestation can continue worsening forever if no one steps in to stop it.THE LOUSE LIFE SPAN WITHOUT A HUMAN HOST
First off, we must note that nits cannot survive without a human host scalp. Without the scalp, the eggs will likely not hatch (incubate) and become nymphs. Both nits and adult head lice require warmth and humidity they get from the human body to survive. Nits that dislocate from their hair shaft will probably die before they have a chance to hatch., as they no longer have the environment they need to survive. They can, however, remain alive after falling off their host, and even hatch. For this to happen, they must have an adequately warm and humid climate surrounding them. Once hatched, newborn nymphs require food in the form of human blood. Nymphs and adult lice can only stay alive for about a day (24 hours) without a food supply. Since they need their human host for food, they’ll only survive approximately 24 hours once no longer attached to a scalp. They may, however, embed in surfaces such as carpets, towels, bedding, garments, furniture, helmets, headphones, or other accessories. Consequently, if their timeline allows, they can pass onto a new host.
