Pubic lice (Phthirus pubis) are tiny parasitic insects that live on coarse human body hair, such as pubic hair.
As well as being found in pubic hair, the lice are also sometimes found in:
- underarm and leg hair
- hair on the chest, abdomen and back
- facial hair, such as beards and moustaches
- eyelashes and eyebrows (very occasionally)
Unlike head lice, pubic lice don't live in scalp hair.
Pubic lice are spread through close bodily contact, most commonly sexual contact.
Symptoms of pubic lice
After getting pubic lice, it can take several weeks before any symptoms appear. Symptoms are the same for men and women and include:
- itching in the affected areas
- inflammation and irritation caused by scratching
- black powder in your underwear
- blue spots or small spots of blood on your skin, such as on your thighs or lower abdomen (caused by lice bites)
Itching is the most common symptom of pubic lice and is an allergic reaction to their saliva. The itching is usually worse at night, when the lice are most active.
What do pubic lice look like?
Adult pubic lice are very small (2mm long) and aren't easy to see. They're a yellow-grey or dusky red colour and have six legs.
Pubic lice are sometimes known as crabs because they have two large front legs that look like the claws of a crab. These are used to hold onto the base of hairs.
The lice lay their eggs (nits) in sacs that are stuck firmly to hairs and are a pale brownish colour. When the eggs hatch, the empty egg sacs are white.
Although pubic lice and lice eggs are small and difficult to see, they may be visible in coarse hair anywhere on your body (apart from hair on your head).
When to seek medical advice
Pubic lice are usually easy to diagnose by examining the affected area. A doctor or nurse may use a magnifying glass to look for signs of the lice, such as pale-coloured eggs or the lice themselves.
Getting tested for STIs
You should be tested for other sexually transmitted infections (STIs) if you have pubic lice through sexual contact. The lice don't transmit HIV or other STIs, but a check-up is usually recommended as a precaution.
Any sexual partners you've had over the last three months will also need to be seen and treated.
How do you get pubic lice?
Pubic lice aren't due to poor personal hygiene. They're usually spread through close bodily contact with an infected person.
The lice crawl from hair to hair, but can't fly or jump. They need human blood to survive, so will only leave the body to move from one person to another.
The most common way pubic lice are spread is through sexual contact, including vaginal, anal and oral sex. Using condoms and other methods of barrier contraception doesn't protect you against pubic lice.
Other types of close bodily contact, such as hugging and kissing, can also spread the lice.
It's also possible – though much rarer – for pubic lice to be spread through sharing clothes, towels and bedding.
Treating pubic lice
Pubic lice can be treated at home with insecticide cream, lotion or shampoo. Your GP or pharmacist can advise you about which treatment to use and how to use it. It's important to follow this advice.
Some treatments only need to be applied to the affected area, but sometimes the whole body must be treated, taking care to avoid the eyes. The treatment usually needs to be repeated after three to seven days.
If the treatment doesn't work, you may need to use another type. This is because pubic lice can develop resistance to some treatments. Your GP or pharmacist will be able to advise you about suitable alternatives.
To prevent re-infestation, anyone you've had close bodily contact with, including any sexual partners you've had in the past three months, should also be treated, even if they don't have symptoms.
Certain groups, such as young people under 18 years of age and pregnant or breastfeeding women, may require a specific type of treatment. Ask your GP or pharmacist for further advice about this.
Applying a lotion, cream or shampoo
In most cases the instructions for using a lotion, cream or shampoo will be as follows:- apply the product to the affected area, particularly any hairy areas, such as your eyebrows, beard or moustache – depending on the product, you might need to apply it to your whole body, including the scalp, neck, ears and face
- be careful not to get the product in your eyes – if you do, rinse your eyes thoroughly with water
- reapply the treatment if you wash any part of your body during the treatment time
- after the treatment time (stated on the packet) has passed, wash the lotion or cream off
- repeat the treatment after three to seven days as instructed
Don't use the medication more than twice. If you think it hasn't worked go to see your GP or pharmacist for advice.
Insecticides used to treat pubic lice may cause skin irritation, such as itchiness, redness, stinging or burning. If you have skin irritation, wash the insecticide off the affected area.
Some aqueous and alcohol-based medications may discolour permed, coloured or bleached hair. Check the patient information leaflet.
The first treatment application will probably kill the lice, but the eggs may not have been destroyed. This means more lice could hatch and the cycle will start again.
Reapplying the treatment after three or seven days will ensure that any lice are killed before they're old enough to lay more eggs.
Check for lice a week after your second treatment, or return to your GP, practice nurse, or sexual health clinic so they can check for you.
Finding empty eggshells (dead nits) doesn't necessarily mean you're still infested as they can remain stuck to the hairs even after treatment.
Treating an eyelash infestation
Eyelash infestations are rare. If your eyelashes are infested, seek specialist advice from your doctor. They'll be able to recommend the correct treatment for you.
You can't use the same insecticide lotion or cream that's used on your body because it will irritate your eyes. Make sure you follow the treatment instructions carefully.
Washing clothing, towels and bedding
Wash clothing, towels and bedding in a washing machine. This should be on a hot cycle (50C or higher) to ensure the lice are killed and to prevent reinfection.
Complications of pubic lice
Sometimes, a pubic lice infestation can lead to minor complications, such as skin or eye problems.
Scratching can irritate your skin, or it could lead to an infection such as impetigo (a bacterial skin infection) or furunculosis (boils on the skin).
Eye infections, such as conjunctivitis, and eye inflammation, such as blepharitis, can sometimes develop if your eyelashes have been infested with pubic lice.
Seek medical advice if you have severe skin irritation or sore eyes.