The School Nurse Lice Battle Plan

Part 8: The Life Cycle of Lice

“My Kid Caught Lice From School....AGAIN!”

Have you ever got a call from a parent that went something like this: “My daughter has head lice...again! I want to know what you are doing about this problem!” Keep in mind that you have seen this child in your office a few times and there are expended nit casings down the length of her long hair spaced out down the strands of hair just like Christmas lights. Those bugs have been in that hair for a while.

Consider the life cycle of the louse:

Step 1: The Nit (Egg): First comes the female louse. She lays (glues) an egg (0.8 mm by 0.3 mm in size (about 0.0315 inches long), oval in shape and usually yellow to white in color) on the hair shaft less than 6mm (a little bit less than a quarter of an inch) from the scalp (often at the base of the hair). This is the sweet spot that allows your head’s warmth to incubate the cemented nit (egg of a louse) for the week it takes for the nit to hatch. The female head louse will lay about 50 to 150 eggs in her lifetime.

If you find nits, consider this: human hair grows about 1/2 inch per month, any nits found on a hair ¼ - ½ of an inch from the scalp will be about 2 weeks old. These eggs are actually either shells or “dead” eggs and will not hatch. Speaking of lice glue…those nits are on their good. I should figure out a way to collect “lice glue” and market the stuff. You’ve heard of Gorilla Glue...Now Comes Nurse Kevin’s LICE GLUE!! Now to find a few thousand head “farmers.” Wanna volunteer for my start-up? NURSE KEVIN"s LICE GLUE And, no...Vinegar will not dissolve the “lice glue.” Do not disregard a nit: From Egg to Egg-Laying: 21 days After the nit comes the nymph.

Step 2: The Nymph: The little baby critter that crawls out of the nit is about the size of a pinhead. They are very tiny. The expended nit (now only a glued-on egg shell) will become more visible as it “rides” the growth of the hair with another nit being glued every 6mm (give or take). Nits in the hair does not mean there is an active case of pediculosis (having head lice).

The nymph will progress very quickly through three molting cycles and become adults about a week after they took their first breath. Molting is the shedding of the exoskeleton. Along with sucking the blood from the scalp and defecating where it feeds, now there are a bunch of exoskeletons laying all about the scalp (again…‘ick factor’). The egg was laid two weeks ago and now the adult lice is looking for a “date” in order to propagate and start laying eggs on her own. The adult female louse only has to mate once and will spend the rest of her life laying her 100 (+/-) eggs. I wish I got that production out of my chickens.

Step 3: The Adult: Ever been to McDonald's? Remember that double-stacked Big Mac? Yea ya do! Don’t be fibbing...I sure do. All those sesame seeds on the top bun really decorate the sandwich don’t they? Well, that’s about how big an adult, female louse is. They are about the size of a sesame seed. The males are a bit smaller and with a wider torso (butt). After 7 days of life, the matured, female louse can lay about 8 nits per day. Considering she will live for about 15 days while feeding (sucking you and your children’s blood from the scalp) many times during the day, and considering that she will lay those 8 nits per day, one louse could turn into about 100 lice inside of a month. I know that’s a long sentence but read it again; 1:100. Granted, not all will survive or be able to “hang-on” during the daily mini tsunami that is the daily hair washing (you are washing your hair often, right?). But, even if 10 of the 100 survive, within a month, you will have a bonafide infestation.

We’ve talked about bugs having “relations,” pooping and ambiguously leaving around their exoskeleton on the host’s head. After about a month of sucking, blood, pooping, and “making-out,” the bug dies and now you have dead bugs on the head (‘ick factor’).

If we school nurses can get the parents to grasp the concept of the life cycle of the lice, then they will better understand the treatment rationales. The “I have to treat her again!” statements may be fewer and farther between if they know that baby lice with hatch from the eggs of the live lice they already killed off in about a week, then they will understand that they need to pick up 2 kits at the pharmacy rather than just one (see the Nurse Kevin Lice Battle Plan).

Maybe use a comparison for the parent to understand. We understand dog years, right? After the nit has been cemented to the hair shaft, that week is comparable to the 9 months of pregnancy. The nit hatches and the nymph grows to an adult during the next week. That’s like coming home from the hospital with a baby and that baby leaving home for college in ONE WEEK. The rest of the bug’s life is like a human adult going from 20-years-old to 80-years-old. Once we redirect the uninformed parent from “my kid caught lice from school and what are you going to do about it?” to “my kid caught lice somewhere and I nipped that in the bud because we have an awesome school nurse at my kid’s school and he (or she) knows her head from a hole in the ground,” then you’ll have fewer cases of head lice...and fewer chances of getting lice yourself (how’s that for a motivator?).



RID contains pyrethrum and NIX contains permethrin. But what does that mean? Is one better than the other at killing lice and what about all those eggs?


You’ve found lice on a head in your home. WHAT THE HECK!? Okay, don’t sweat. You’ve got this. Read this LICE BATTLE PLAN and get them bugs gone!!


Learn more about lice. You have an 2-3% chance of lice coming into your home this year. The more you know about these pests the better prepared you’ll be.

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