Pubic lice (crabs): symptoms, treatment and preventing spread in the UK

Pubic lice are small parasitic insects. The NHS says they are about 2mm long and grey-brown in colour, which makes them hard to spot, although sometimes they can be seen in the hair. They most often live in the pubic hair around the penis or vagina, but they can also be found in hair on the chest, armpits, face and eyelashes. They do not affect hair on the head.

NHS inform adds that they need human blood to survive, so they generally leave the body only to move from one person to another, and that they do not live on animals such as cats or dogs. It also emphasises that pubic lice are not linked to poor personal hygiene.

Because they are usually passed on during sex, pubic lice are classed as a sexual health issue, although they are not an infection in the usual sense. They are an infestation.

NHS inform says it can take up to 3 weeks after contact before you notice any symptoms. The most common symptom is itchy red spots, and the itching is caused by an allergy to the lice saliva or poo. It can take 1 to 3 weeks for itching to develop after the first infestation, and it is usually worse at night.

Other signs listed by the NHS include small red or blue spots on the skin from lice bites, white or yellow dots attached to the hair (lice eggs) and dark red or brown spots in underwear (lice poo). NHS inform adds crusty or sticky eyelashes if they are infected.

• Itching in the pubic area, usually worse at night.

• Small red or blue spots on the skin.

• White or yellow dots attached to hair.

• Dark red or brown spots in underwear.

• Crusty or sticky eyelashes if lice are present there.

The NHS advises going to a sexual health clinic or seeing a GP if you think you might have pubic lice. It adds that if you are sure you have them, you may be able to get treatment from a pharmacist. NHS inform says you can be checked for free at a sexual health service or by your GP practice, and that you can buy treatment over the counter, although a pharmacy cannot diagnose the infestation.

Pubic lice are not an emergency. If treatment has not worked after the course has been repeated, or lice are on the eyelashes, speak to a clinic or GP because the approach differs.

NHS inform states that there is no test for pubic lice. A doctor or nurse will check the hair for lice, including the pubic hair around the penis or vagina and other areas that could be affected such as the armpits, chest or eyelashes. They may use a comb and magnifying lens.

If you may have caught the lice during sex, you may be asked about sexual partners. The NHS says you may also be offered testing for other sexually transmitted infections, and NHS inform recommends testing for gonorrhoea, chlamydia and syphilis if pubic lice are diagnosed.

The NHS says the main treatments are medicated creams or shampoos that kill the lice. You usually apply them to the whole body, but not the eyebrows or eyelashes, leave them on for 12 hours or overnight, and repeat after a week. You may be asked to return a week after finishing treatment to check it has worked.

The British Association for Sexual Health and HIV (BASHH) says permethrin 5% cream is licensed for pubic lice and is safe and effective on pubic and body areas other than the eyelashes, and that it should be left on for 12 hours. Malathion 0.5% aqueous solution, left on for 12 hours, is a second-line alternative, and with both a second application 7 days later is recommended. For lice on the eyelashes it advises an inert occlusive eye ointment twice a day for 8 to 10 days and not petroleum jelly, which can irritate the eyes.

NHS inform adds that some pubic lice can be resistant to treatment, so if symptoms do not settle you may need more than one type of treatment, and that creams and lotions that are fine elsewhere are not safe near the eyes.

While being treated, the NHS advises washing clothes and bedding on a hot wash of 50C or higher, having them dry cleaned, or putting them in a plastic bag for at least 2 weeks, and vacuuming the mattress. It advises not sharing clothes, bedding or hygiene products such as razors, and not having close body contact, including sexual contact.

NHS inform says to avoid sex until you and your partner have both finished treatment including any follow-up. Condoms and other contraception do not protect against pubic lice, though the NHS still recommends condoms because they reduce the risk of other sexually transmitted infections.

NHS inform says you can be checked for free at a sexual health service or by your GP practice, and treatment can be bought at a pharmacy. Many people use a pharmacy first when the diagnosis is clear.

Private sexual health clinics and online services also exist, mainly offering quicker appointments and broader STI testing. The treatments are the same, so the key points are to complete the second application and to ensure partners are treated.