How to check for head lice

What is Head Lice?

Head lice are tiny six-legged blood-sucking wingless parasites that live in your hair.  Their bodies are translucent with a hard eco-skeleton shell.  Lice have 6 legs; each leg is equipped with a crab-like claw enabling them to grab onto a single strand of hair. All 6 legs are at the top of the body so lice can't jump. They can vary in color from greyish white to reddish brown. A louse will tend to adapt to the color of the hair that they are living in. A single adult hair louse is usually 2 – 3 mm long.  Adult female lice are usually longer and wider than the male lice.

Lice eggs attached to hair shaft

Where Does Head Lice Come From?

​Head Lice has been around for thousands of years.  If you look in the bible you will find mention of lice under Exodus 8:16, 8:17, 8:18, PSA 105:31, and Jeremiah 43:12. In Brazil they have uncovered a mummy with nits in the hair dating back 10,000 years. Lice combs have been unburied dating back to 1,500 B.C. Believe it or not, evidence of insects that look like modern lice took up residents on the bodies of dinosaurs.  Scientists have discovered fossils dating back 100 million years in the Cretaceous period.

How Do We Get Head Lice? How Are Lice Spread?

In almost all cases, lice are transmitted from one human head to another. A louse has antennae located in front of their eyes. This enables them to detect odor, humidity, and temperature. Once a louse feeds on a particular blood type they must stay with that blood type. Refer to the chart below: 

Head Lice blood type sensitivity


The chances of contracting head lice from your environment are about 2%.   It is always good practice to communicate with people you have been in close contact with and let them know they should check their heads for lice.  We would recommend informing anyone that you have had close contact with within the previous 2 weeks. This will decrease the chances of contracting lice again.

How Many Eggs Will A Female Louse Lay in a Day?

The female louse only needs to mate once in her lifetime and will remain pregnant until she dies - her lifespan is typically 30-35 days.  24 hours after mating the female will begin to lay her eggs. A single female louse will lay 4 to 5 eggs (nits) in a cluster twice a day. When the eggs are laid the female louse will secrete a liquid over the nits that cements them to the hair shafts. A healthy female will lay approximately 200 eggs during her lifetime.

How fast does lice accumulate?

  • Week 1: 1 adult | 60 eggs | 0 nymphs
  • Week 2: 1 adult | 60 eggs | 60 nymphs
  • Week 3: 61 adults | 3660 eggs | 60 nymphs
  • Week 4: 61 adults | 3660 eggs | 3660 nymphs
  • Week 5: 3660 adults | 219,600 eggs | 3,660 nymphs

Head Lice Life Cycle:

The female louse will begin to lay eggs within 24 hours of getting pregnant.  She will lay 4 - 5 eggs 2x a day until she dies, which is approximately 20 days after becoming an adult.  The eggs are cemented on the hair shaft closest to the scalp.  7 - 10 days after being laid the egg hatches and a baby louse emerges.  The baby louse (aka nymph or instar) will go through 3 stages, each stage lasting 3 to 4 days.  I like to refer to each stage as baby toddler teenager.  Once the female becomes a teenager, on the 3rd or 4th day she will mate.

Head Lice Life Cycle

Can Head Lice Transmit Diseases?

Head lice have a relatively short lifespan of 30-35 days, and they typically remain on a single host for their entire existence. As a result, the chances of these parasites transmitting diseases are exceedingly low. Nevertheless, it's important to note that secondary infections can arise from scratching and inadequate treatment, which may pose health concerns.

Do household pets get lice?

No - pets cannot get human head lice.  There are over 3000 species of lice, but they are host-specific - meaning they cannot transfer to/from different species.  In other words, the head is lice human-specific and pet lice would be in the form of fleas.

Does race/ethnicity play a role in contracting head lice?

Head lice do not discriminate - as long as you have hair on your head, you can get head lice.  However, because an African American hair strand is a different shape, it is somewhat difficult for lice to attach to the hair strand, but this does not exclude African Americans from contracting head lice.

What are the common symptoms of head lice?

  • Rash-like bumps on head (behind ears, crown), neck and shoulders.
  • Itching - sometimes more at night (as lice are nocturnal)
  • Increased itching day by day
  • Immune system lowered due to lack of REM sleep 
  • First-time infestations may not show any signs for up to 2 weeks

Why do we itch from lice bites?

A single louse will feed every 3-4 hours.  When they bite us, they secrete a small amount of saliva.  As this saliva builds up due to numerous bites, most of us will develop an allergic reaction to the lice saliva in the form of itching.  The itch will be more prevalent in the morning and at night and will increasingly get worse the longer the lice is left untreated.  A small percentage of the population is asymptomatic to the lice bites and will not react.  Once you have contracted lice the first time, any future infestations will cause symptoms to surface earlier.


Will head lice go away on its own?

There is a slim possibility that an unfertilized female or a lone male.  In most lice cases it is required to treat as you wouldn't know if eggs were laid or not.



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