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what causes lice

How do you get lice?

How does lice start? A friend or coworker gets lice, or your child’s school sends home a note, and suddenly you can’t stop thinking about lice. How do you get head lice? Do you have them? Does your child? How do you know? How do you prevent them?


Familiarizing yourself with what causes head lice, symptoms, prevention measures, and treatment options (and learning how to separate lice fact from lice myth) will help you make the best decisions.


What are lice?

A louse is a tiny parasite that feeds on human blood. (“Lice” is the plural form of “louse.”) They are wingless insects that spread through close contact and shared personal items. Head lice are the most common type of lice and infect children more often than adults.


Types of Lice

There are three types of lice:

Signs you have lice

How to know if you have lice

How do I know if I have lice? There are multiple ways how to know if you have lice. Here are some signs you have lice:

Why do lice itch?

Lice itch because their bites cause an allergic reaction. Insatiable itching is the most familiar symptom of a lice infestation. Head lice itching occurs on the scalp, around the ears, and along the neck—just below the hairline.


How long can you have lice before it itches?

Lice itching may not become noticeable for four to six weeks, especially if the infestation is light or if it is the first time the individual has had lice. If you think you notice a louse, or if the individual feels “tickling” on the scalp or skin, don’t ignore it just because the itching has not (yet) started.


How long do lice bites itch?

Each louse bite (head lice bites) will itch for several days, so even after lice have been treated and removed, the itching may persist. Doctors often recommend an over-the-counter allergy medication to help ease the itching and reduce scratching.


5 Other Lice Symptoms & Signs of Lice

How to tell if you have lice

Itching is the most widely recognized way how to know if you have lice, but it’s not always the first sign of lice. Catching an infestation early often means being familiar with other lice symptoms as well. Here’s how to tell if you have lice:

Head Lice Symptoms – Signs of Head Lice


What causes lice & where do lice come from?

Lice most commonly spread from one person to another by close contact, such as head to head contact. Head and pubic lice usually spread by hair-to-hair or bodily contact. They can also spread by sharing personal items, such as hats, combs, and pillows. These lice, however, cannot live long off of a host, so spreading via personal items is much less common.


Head lice are not easily washed away with normal shampoos and the insects are impartial to clean or dirty hair. Poor hygiene is not what causes lice. 


Body lice do not live on the human body, so they can be more easily spread by sharing clothes, bedding, or upholstered furniture. They are also spread by storing clothes or bedding near infested clothes or bedding.


Pubic lice are spread by sexual contact with an infected individual. 


Lice cannot jump or fly, so any kind of lice infestation is caused by physical contact between individuals or personal items.


Lice only feed on humans, so pets cannot bring them into the house.


By becoming informed on what causes lice you can better defend against it.


Lice Prevention

The only way to prevent lice is to avoid contact with infested individuals and items. As a lice infestation is often invisible for several weeks, however, it’s almost impossible to completely prevent lice. 


Reasonable precautions include:



Lice Treatment Options

The best form of lice prevention is preventing the spread once you know someone in your family does have lice. 



Additional considerations for head or pubic lice:



Learn more about removing head lice for good → 


Additional considerations for body lice:



When to See a Doctor for Lice

If you think you or a loved one has lice, but you aren’t sure, make an appointment with your doctor. Doctors have ready access to special lights and combs that can make it easier to identify an infestation.


Additionally, if over-the-counter lice treatment solutions are ineffective for head lice, you may be dealing with super lice. Most head lice cases in the U.S. are now a strain of super lice that are resistant to permethrin and/or pyrethrin—the two main ingredients in traditional OTC treatments. A doctor can write a prescription for stronger lice medication.


Stop Lice Itching

Lice make your head itch because of an allergic reaction to louse bites, but quick and effective treatment can prevent further spreading and ease symptoms as fast as possible.


Understanding a full range of lice symptoms, causes, prevention methods, and treatment options is the first step to dealing with lice appropriately. Take symptoms and warning signs seriously, do what you can to prevent lice from spreading, and start treatments quickly.


The next step is to keep an over-the-counter treatment option on-hand so that if an infestation does occur in your home, you can deal with it immediately—without running to the pharmacy or making a doctor’s appointment.

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