Pubic lice are tiny insects that live on humans, usually in the pubic hair. They are passed on through close body contact, such as when having sex. Infestation with pubic lice can cause itching but not everyone affected has symptoms. Treatment involves using an insecticide lotion or cream to kill the lice. If you have caught pubic lice from a sexual partner, you should be tested for other sexually transmitted infections (STIs).
Body lice are also passed on in close contact. They mostly occur in cold climates and in overcrowded areas where there is poor sanitation and a high rate of poverty. Being unable to wash regularly or wearing the same clothes for a long time increases the chance of catching body lice, so homeless people are at increased risk.
What are pubic lice and body lice?
Pubic lice are tiny insects about 1-2 mm long (smaller than the head of a match). Their medical name is Phthirus pubis and they are grey or brown in colour. Sometimes they are called crabs because their second and third pairs of legs have crab-like claws. These claws are used to hold on to hairs tightly. Lice are blood-sucking insects which survive by feeding on tiny amounts of your blood, which they obtain through your skin. Female lice lay eggs (also called nits) which are smaller than a pinhead. These eggs stick to the hairs in which the lice live. The eggs hatch into lice after 6-10 days. A female louse can lay up to 300 eggs in her lifetime of 1-3 months.
Pubic lice live in hairy areas of the body. Because they prefer thick coarse hair, pubic lice commonly affect the pubic hair. However, they may also affect body hair around the back passage (anus), underarms, beard, chest and, rarely, eyebrows and even eyelashes.
Pubic lice only affect humans. They can't be caught from, or passed to, animals. Note: pubic lice do not live in the hair on your head, as scalp hair tends to be softer and finer, and the lice can't hold on to these hairs. Head lice are a different type of louse (called Pediculus humanus capitis).
Body lice are slightly longer than pubic lice (about 3-4 mm) but have a narrower body. Their medical name is Pediculus humanus. They are also known as clothing lice because the lice and their eggs can be found in the seams of clothing. Body lice can be found anywhere in the body but tend to avoid the scalp, except at the margins.
How do you get lice?
You need close body contact to pass pubic lice on to others. Usually pubic lice are caught by having sex with a person who already has a pubic louse infestation.
It is possible to 'catch' pubic lice through close non-sexual physical contact with an affected person - such as kissing someone who has lice in their beard.
Pubic lice and their eggs attach very strongly to hair; they neither simply wash or brush off, nor do they fall off. They also cannot survive for long without a human 'host' to feed from. This means that you are extremely unlikely to catch pubic lice from clothing, bed linen, shared towels or toilet seats.
You can catch body lice by coming into close physical contact with someone who has lice. This need not be sexual contact. You can also catch it from lice-infested clothing, bedding or towels. Body lice are mainly seen in homeless people who are unable to wash frequently or change their clothes regularly.
What are the symptoms of lice?
- The main symptom is generalised itching in the affected areas, usually in the pubic hair region. Itching may take between one and three weeks to begin after you become infected. Itching is usually worse at night, when the lice feed. It is due to a sensitivity to louse saliva.
- Itchy red 'bumps' on the skin, in the hair-covered areas, may appear.
- Faint blue spots may appear on the skin. This occurs where the lice have been feeding.
- Skin irritation and scratching may cause redness or a rash in affected areas.
- You may develop eye inflammation if your eyelashes are affected.
- You might notice really tiny dark brown specks in your underwear or your skin - this is lice poo (faeces).
- Some people have no symptoms but can still pass lice on to others without realising they are doing so.
Some people do not get any symptoms but notice the lice or nits on their body or clothes. Itching at night is common and usually occurs on the trunk, the armpits or the groins. This happens because body lice usually live in clothing during the day, only moving on to the skin when feeding on the person's blood. As with pubic lice, small red lumps and blue spots can occur.
What is the treatment for lice?
Pubic lice infestation is treated with insecticide specially formulated to be used on the human body. It kills the pubic lice. The whole body should be treated, twice - seven days apart. You should avoid getting insecticides in the eyes.
The two commonly used insecticides to treat pubic lice are malathion lotion and permethrin 5% cream. Water-based (aqueous) products are preferred over alcohol-based treatments (which may cause even more skin irritation). They are easy to apply and normally work well if used properly. The following is a general guide, giving tips for success:
- Malathion is suitable for all people.
- Permethrin is NOT usually used if you are under 18.
- You should apply the lotion or cream to all your body, including the scalp. This is because the lice can spread and affect many parts of your body and sometimes even the scalp. You should pay particular attention to hairy parts of your body, especially to pubic hair, hair around your back passage (anus), beards, moustaches and eyebrows. Note: this advice is based on national guidelines and may be different to what is said on the insecticide packet. The packet may say only apply from the neck down - but experts recommend that the whole body be treated (taking care to avoid getting the insecticide in the eyes).
- An average adult needs about 100 ml of lotion or 20-30 g of cream to apply to the whole body.
- Apply lotion or cream to cool, dry skin. If you have a hot bath or shower, wait until the skin cools down and is fully dry before applying.
- You should leave the lotion or cream on for the full recommended time and then wash it off. Malathion should be left on for 12 hours (overnight) and then washed off. Permethrin 5% dermal cream should be left on for 24 hours and then washed off.
- If you wash any part of your body during the treatment period, you should reapply the lotion or cream again to the washed areas.
- You do not need to shave the affected areas. The lotion or cream will clear the lice.
- Some people advise washing bed linen, towels and clothes (particularly underwear) which have been used since a week before symptoms started. There is no good evidence that this is necessary but some people prefer to do it.
- If your eyelashes are affected, ask a doctor for advice on how to treat these areas. Simple eye ointment or Lacri-Lube® ointment is greasy, like Vaseline®, and often applied to the eyelashes with cotton buds to suffocate the lice.
- Tell your doctor or pharmacist if you are pregnant or breast-feeding, as some treatments may not be suitable.
Re-apply the same treatment after seven days. Although lice are usually killed by one application, not all eggs may be. The second application makes sure that any lice that hatch from eggs that survived the first application will be killed before they are old enough to lay further eggs. Note: this advice is based on national guidelines and may be different to what is said on the insecticide packet. The packet may say that one application is sufficient - but experts recommend the two applications, seven days apart.
Because body lice mainly live in clothing and bedding, applying treatment to the skin is less important. The main treatment is directed at destroying the nits and lice in clothing and bedding. This can be achieved by laundering in hot water (at least 130°F), ironing with a hot iron, drying in a hot dryer or dry cleaning. If there are lots of lice present an insecticide may need to be applied directly to the body.
Clothing and bedding are sometimes treated with insecticide if there is an outbreak in a community.
Do family and friends need treatment?
Recent close contacts and sexual partners within the previous three months should be examined for lice and treated if infected. Remember, you can have pubic lice without symptoms.
People in contact with the body, clothing or bedding of a person with body lice should be examined for lice themselves. Their clothing and bedding should also be treated and they may need to step up their hygiene routine.
Some other points about pubic lice
- Itching often takes a few days to settle after successful treatment.
- Consult a doctor if symptoms persist after the second application of lotion or cream. This is because pubic lice sometimes become resistant to one type of insecticide and a different insecticide may be needed.
- Avoid close body contact with others until you finish the second treatment application.
- If you got pubic lice from a sexual contact then you should be tested for other STIs. Your doctor may do this or refer you to a genitourinary medicine (GUM) clinic.
Further reading and references
; NICE CKS, December 2011 (UK access only)
; British Association for Sexual Health and HIV (2007)
; Pubic lice (Pthirus pubis): history, biology and treatment vs. knowledge and beliefs of US college students. Int J Environ Res Public Health. 2009 Feb6(2):592-600. doi: 10.3390/ijerph6020592. Epub 2009 Feb 6.
; NICE Evidence Services (UK access only)
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