Pubic lice

Published by Bupa’s Health Information Team, August 2011.

This factsheet is for people who have pubic lice, or who would like information about them.

Pubic lice – also known as crabs – are insects that live in pubic hair. They can also infect other hair on the body, such as the eyebrows and eyelashes.

About pubic lice

Pubic or crab lice (Phthirus pubis) are wingless insects that are dark grey or brown in colour and about 2mm long when fully grown. They generally live on the coarse hair around your genitals and anus, but you can also get them in your eyelashes and in the hair on your chest, abdomen (tummy), back, armpits or face. Pubic lice feed off human blood.

Female lice lay eggs that are smaller than a pinhead and attach them to the bottom of your hair fibres. The eggs hatch about six to 10 days later. When the lice hatch, they leave empty shells, called nits, which stick to your hair. You may mistake them for flakes of dry skin – or dandruff – but unlike dandruff, nits stick to your hair and you won't be able to remove them with normal shampooing. Pubic lice are different from head lice, which you get on your scalp.

People of any age can get pubic lice, but they are most common in young adults.

Symptoms of pubic lice

It can take several weeks after getting pubic lice to have any symptoms, or you may not have any symptoms at all. If you do, the main symptom is itching, particularly at night. The itching is caused by an allergic reaction to louse droppings or saliva. Other signs of having pubic lice include: 

• your skin looking redder than usual
• what look like flakes of skin in your hair – these are nits stuck to your hairs
• black powdery spots in your underwear – due to louse droppings or blood spots
• blue spots or specks of blood on your skin – from lice bites

You may also be able to see lice moving in your hair.

If you have any of these symptoms, see your GP or visit a sexual health clinic.

Complications of pubic lice

If you scratch a lot, your skin can become broken and inflamed, and can get infected. Try not to scratch your skin to prevent getting an infection and get treatment for pubic lice as soon as possible.

If your eyelashes are infected with lice, it can sometimes cause an eye infection called conjunctivitis or inflammation of your eyelids (blepharitis).

Causes of pubic lice

Pubic lice are often passed between people through sexual or intimate contact, as the lice crawl from hair to hair – but they can't fly or jump.

It may also be possible for the lice to live on your bed sheets, towels or clothes. They may occasionally be passed on this way, but more research is needed to know for sure.

If you have genital contact with an infected partner but don't have sex, you can still get pubic lice. If you have more than one sexual partner or frequently change sexual partners, you’re more at risk of getting pubic lice.

Diagnosis of pubic lice

If you think you may have pubic lice, visit your GP or a sexual health clinic. You can contact a sexual health clinic yourself and make your own appointment – you don’t need to be referred by your GP. Your visit will be confidential and you don't have to give your real name. Details aren’t sent to your GP without your consent.

Your doctor or nurse will ask about your symptoms and examine you. He or she will search for any lice, eggs or blue spots to diagnose pubic lice.

You may also be asked to have some tests to see if you have any other sexually transmitted infections (STIs). This may involve having a blood test.

You might not get visible signs or symptoms of pubic lice straight away, so you may be asked to return for another appointment at a later date.

Treatment for pubic lice

You will need to get treatment for pubic lice as it’s unlikely they will go away on their own.

There are a range of medicines to treat pubic lice including lotions and shampoos that contain the insecticides malathion (eg Derbac-M) and permethrin (eg Lyclear). You can buy some of these over the counter from a pharmacy, or your doctor can prescribe them for you. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your doctor or pharmacist for advice. If you’re pregnant or breastfeeding, or are under 18, check with a pharmacist or your doctor before using these medicines.

With most of the medicines you will need to apply the preparation for 12 hours then wash it off. It’s important to treat all your body hair (including your beard if you have one) and your eyebrows. Reapply the lotion or shampoo seven days later to ensure any lice that may have hatched after the last application are also killed. Be careful not to get the lotion in your eyes and don’t use the treatments on broken or infected skin. If you have pubic lice in your eyelashes, apply petroleum jelly (eg Vaseline) twice a day for 10 days. You can also use a lower-dose version of permethrin.

Your doctor may also prescribe you an antihistamine, such as chlorpheniramine, to help ease any itching.

Nits can stick to your hair and not go away after treatment, but you can remove them with a fine comb. However, the comb won’t remove any pubic lice that are left. You can also try to remove them with a pair of fine tweezers. If the lice come back, you may need to have more treatments.

Don’t use treatments that are designed for removing head lice as they are too harsh for your genital area.

Prevention of pubic lice

If you have pubic lice, wait until your doctor gives you (and your partner) the all clear before having sex (or any close contact) again. It’s important to contact your current or most recent sexual partners to inform them that they may have pubic lice too. This will help to prevent them passing the infection on to others if they take the correct preventive measures. Clinics can send anonymous notifications on your behalf if you prefer.

As pubic lice are often passed from person to person through sexual contact, you can reduce your chances of getting them by reducing your number of sexual partners. Using condoms for vaginal, anal and oral sex can help prevent most STIs, but they can't protect you from getting pubic lice.

As lice may possibly live in your bedding and clothing, wash these items at a high temperature (50°C) or dry clean them to kill the lice. This may help to prevent you getting infected again.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.