Head lice
What are the symptoms of head lice?
You can have head lice without knowing it, as there are often no symptoms.
This means it can take weeks or even months before you realize that you or someone in your family has head lice.
1
Source:
Dodd CS.
Interventions for treating head lice (Cochrane review).
In: The Cochrane Library. Wiley, Chicester, UK.
Dodd CS.
Interventions for treating head lice (Cochrane review).
In: The Cochrane Library. Wiley, Chicester, UK.
But you may occasionally notice some of the following symptoms.
Some people get an itchy scalp when they have head lice. We don't know exactly how many people with head lice get an itchy
scalp because there hasn't been much research.
2
3 This is difficult to study because just the thought of head lice makes some people itch.
Source:
Mumcuoglu KY, Klaus S, Kafka D, et al.
Clinical observations related to head lice infestation.
Journal of the American Academy of Dermatology. 1991; 25: 248-251.
Mumcuoglu KY, Klaus S, Kafka D, et al.
Clinical observations related to head lice infestation.
Journal of the American Academy of Dermatology. 1991; 25: 248-251.
Source:
Courtiade C, Labreze C, Fontan I, et al.
Pediculosis capitis: a questionnaire survey in 4 schools of the Bordeaux Academy 1990-1991.
Annales de Dermatologie et de Venereologie. 1993; 120: 363-368 [in French].
Courtiade C, Labreze C, Fontan I, et al.
Pediculosis capitis: a questionnaire survey in 4 schools of the Bordeaux Academy 1990-1991.
Annales de Dermatologie et de Venereologie. 1993; 120: 363-368 [in French].
It's the louse's saliva that can cause itching. Head lice inject saliva into your blood as they feed. The saliva contains
chemicals that stop your blood from clotting.
Your body's
immune system (which protects your body against
infection) detects the saliva in your blood. Because the saliva is foreign to your body, your immune system responds by releasing chemicals
into your bloodstream to attack the saliva and get rid of it.
immune system
The immune system is made up of the parts of the body that are devoted to fighting infection. The body is constantly being threatened by infections from things like bacteria, viruses and parasites. The immune system fights these infections in different ways. At the microscopic level, the immune system uses antibodies and white blood cells, which travel in the blood and target infectious agents, such as bacteria. These microscopic parts of the immune system either kill the infectious agent directly, or take it to other parts of the body, like the spleen, where it can be dealt with. The lymph nodes are another important part of the immune system. Within them, white blood cells filter through the foreign material that has entered the blood, to see if there are any infections. When you have a swollen gland during a cold, this is actually a lymph node that is reacting to the infection. Unfortunately, it is possible for the immune system to become confused and to use its destructive powers to target healthy parts of the body. Diseases that result from this type of situation are called autoimmune diseases.
The immune system is made up of the parts of the body that are devoted to fighting infection. The body is constantly being threatened by infections from things like bacteria, viruses and parasites. The immune system fights these infections in different ways. At the microscopic level, the immune system uses antibodies and white blood cells, which travel in the blood and target infectious agents, such as bacteria. These microscopic parts of the immune system either kill the infectious agent directly, or take it to other parts of the body, like the spleen, where it can be dealt with. The lymph nodes are another important part of the immune system. Within them, white blood cells filter through the foreign material that has entered the blood, to see if there are any infections. When you have a swollen gland during a cold, this is actually a lymph node that is reacting to the infection. Unfortunately, it is possible for the immune system to become confused and to use its destructive powers to target healthy parts of the body. Diseases that result from this type of situation are called autoimmune diseases.
infection
You get an infection when viruses, bacteria, fungi or other tiny organisms get into your body. These bugs are so tiny that you can't see them without a microscope. For example, an infection in your airways causes the common cold. And an infection in your skin can cause rashes such as athlete's foot.
You get an infection when viruses, bacteria, fungi or other tiny organisms get into your body. These bugs are so tiny that you can't see them without a microscope. For example, an infection in your airways causes the common cold. And an infection in your skin can cause rashes such as athlete's foot.
Some of the chemicals act at the site where the saliva got into your body, and it's these chemicals that make you itch. It
can take up to three months for the itching to start.
On most scalps, bites from head lice are almost impossible to spot. But if you know what you're looking for, you may be able
to see them. They are small and round (about the size of a pinprick) and red from the scab that has formed over the bite.
Occasionally, bites can become infected (see below) and the scabs can become crusty and itchy.
You may notice nits in the hair. These are the shells (also called casings) of the head lice eggs, and they are usually near
the scalp, where the eggs are laid for warmth and moisture. Unhatched eggs are colorless and therefore very difficult to spot.
But once the baby head lice hatch, the casings that are left behind look white and are easier to see.
As the hair grows, the eggs or their casings move away from the scalp. If you see nits more than a half inch from the scalp,
it means either they have hatched already or the eggs are not going to hatch.
Seeing nits is not a sign that you currently have head lice, since they may be empty shells or dead eggs. But they are a sign
that you need to check your hair for head lice. You have to find a live head louse on your hair to be sure you have them.
4
Source:
Burgess IF.
Human lice and their control.
Annual Review of Entomology. 2004; 49: 457-481.
Burgess IF.
Human lice and their control.
Annual Review of Entomology. 2004; 49: 457-481.
You might see a head louse crawling through your child's hair or your own hair. If you have not seen head lice before, you
will find it difficult to spot one. You're more likely to come across a head louse or its discarded skin when you comb the
hair. But unless you know what you're looking for, you might miss these signs. To learn about what head lice look like, see
What are head lice?
Head lice are rarely more than a nuisance. But, occasionally, the bites can become infected. This is more likely to happen
if you scratch your head and pull the scabs off bites. If the head lice in your hair are carrying
bacteria (germs), these can get into the wound.
bacteria
Bacteria are tiny organisms. There are lots of different types. Some are harmful and can cause disease. But some bacteria live in your body without causing any harm.
Bacteria are tiny organisms. There are lots of different types. Some are harmful and can cause disease. But some bacteria live in your body without causing any harm.
One of the most common infections from head lice is
impetigo of the scalp. This is a skin infection that head lice can pick up from one person, carry on their body and transmit to someone
else. Impetigo causes crusty and very itchy scabs. Impetigo needs to be treated with
antibiotics.
impetigo
Impetigo is a skin rash, usually on the face, that is caused by certain types of common bacteria. The rash typically appears dry and crusty, and has a golden color. It can be cured with antibiotic medications.
Impetigo is a skin rash, usually on the face, that is caused by certain types of common bacteria. The rash typically appears dry and crusty, and has a golden color. It can be cured with antibiotic medications.
antibiotics
These medications are used to help your immune system fight infection. There are a number of different types of antibiotics that work in different ways to get rid of bacteria, parasites and other infectious agents. Antibiotics do not work against viruses.
These medications are used to help your immune system fight infection. There are a number of different types of antibiotics that work in different ways to get rid of bacteria, parasites and other infectious agents. Antibiotics do not work against viruses.
Impetigo is also easily passed on (highly contagious). If you have crusty or itchy scabs on your scalp, you should see your doctor right away. You should get
rid of the head lice at the same time you're taking antibiotics for the infection.
If head lice go untreated for a long time (say, 12 months to 18 months), they can make you feel generally low and tired.
2 This is because your immune system becomes worn down after this time. Since head lice are usually treated these days, this
is now rare.
Source:
Mumcuoglu KY, Klaus S, Kafka D, et al.
Clinical observations related to head lice infestation.
Journal of the American Academy of Dermatology. 1991; 25: 248-251.
Mumcuoglu KY, Klaus S, Kafka D, et al.
Clinical observations related to head lice infestation.
Journal of the American Academy of Dermatology. 1991; 25: 248-251.
Some people say that head lice leave a gritty black powder on their pillow. But there is no evidence for this. The head lice
do leave tiny bits of blood they've digested, but the amount is very small (unless the infestation is very heavy).
Any waste from the head lice will normally be dissolved in sweat, especially at night. Children sweat more than adults, and
this means their pillowcases may become dirty more quickly than usual.
Sources for the information on this page:
- Dodd CS.Interventions for treating head lice (Cochrane review).In: The Cochrane Library. Wiley, Chicester, UK.
- Mumcuoglu KY, Klaus S, Kafka D, et al.Clinical observations related to head lice infestation.Journal of the American Academy of Dermatology. 1991; 25: 248-251.
- Courtiade C, Labreze C, Fontan I, et al.Pediculosis capitis: a questionnaire survey in 4 schools of the Bordeaux Academy 1990-1991.Annales de Dermatologie et de Venereologie. 1993; 120: 363-368 [in French].
- Burgess IF.Human lice and their control.Annual Review of Entomology. 2004; 49: 457-481.
This information was last updated on May 11, 2009
This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment.
© BMJ Publishing Group Limited 2009. All rights reserved.
© BMJ Publishing Group Limited 2009. All rights reserved.
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