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Treatment of crabs (pubic lice)

By Dr Ananya Mandal, MD

Crabs or pubic lice affect a person who comes in direct bodily contact with someone who is infected with the tiny parasites.

The parasites are tiny insects that live off human blood and infest the pubic hair or other coarse and thick body hair like those of the armpits, legs, chest, abdomen, back etc.

The treatment is based on the use of de-lousing medications in the form of lotions, creams and shampoos. However, pubic lice infestation commonly tends to recur if the therapy is inadequate or if the infected sexual partner is not treated.

Treatment for pubic lice includes medicated creams, lotions and shampoos, washing all clothing, bed linen and so forth. 1-7

Medicated creams, lotions and shampoos

These are available over the counter at the pharmacist’s or prescribed by the doctor. The directions on the pack must be followed closely for best results.

The medication is applied to the affected area and sometimes the whole body barring the eyes and the scalp.

Pubic lice usually do not affect scalp hair. This is because the lice prefer coarse and thick hair while those on the head are softer, thinner and finer.

The preparation needs to be applied with a cotton swab or wool even on the hair of the legs, thighs, abdomen, back, around the anus, beard and moustache (if infected), armpits etc. An adult approximately needs around 100ml of lotion or 30–60g of cream for one application.

The most commonly used medicated preparations include malathion 0.5% aqueous lotion and permethrin 5% dermal cream. Lotions tend to be more effective than shampoos.

Aqueous (water-based) products are preferred over alcohol-based treatments. The latter may cause even more skin irritation. Most of these are rinsed off after 10–15 minutes and some may need to be left on for longer.

Malathion lotion is left on for 12 hours or overnight and permethrin cream is left on for 24 hours. If any part is washed, the cream needs to be reapplied. The preparation is washed off after the correct duration has passed.

The treatment is usually repeated after 3–7 days. The medication is not to be used more than twice. If the infection persists, the preparation may be changed to another.

After a course of therapy the infection is usually cured. Itching may continue for a few days even after the infection goes away. In addition, inspection may reveal empty egg shells of the lice that have been killed. This may persist for a while after cure. A special comb may be used to remove the nits.

Shaving the affected area – not required

Shaving off the affected hair in the pubic region or other areas of the body is usually not required.

Washing of clothing, bed linen etc.

All clothing, bed linen, towels etc. need to be machine washed in a very hot cycle (50°C or higher) to kill the lice and avoid recurrence of the infection.

Items of use and linen that cannot be washed needs to be put in sealed packages and left for at least 2 weeks. This kills all the newly hatched nymphs as well as the adult lice if present within the linen.

Check-up for other sexually transmitted infections (STIs)

A check up for other sexually transmitted infections (STIs) is usually suggested in persons with pubic lice infestation. After a week of therapy the patient needs a check up to ensure that pubic lice have gone.

Treatment for sexual partners

The sexual partner of the affected person needs to be evaluated for pubic lice and other STIs and treated adequately. This prevents a chance of recurrence of the infection in the affected person.

It is advised that the affected person does not have any sexual intercourse, including vaginal, anal or oral sex, or close body contact with any one of their sexual partners until they or both the partners have undergone full therapy and are declared cured of the infection. This helps in prevention of recurrence and reduces chances of transmission to other individuals.

Caution in women who are pregnant or breastfeeding

Women who are pregnant or breastfeeding need caution with the medication commonly used to treat pubic lice and may need to consult their physician before they undertake therapy.

For pregnant and breastfeeding mothers Permethrin cream is safe to use. However, the cream needs to be washed off completely before each feed if the woman is breastfeeding and reapplied if necessary. (1, 2, 7)

Children under the age of 18 with pubic lice infestation also need to consult their doctors before applying any of the over-the-counter medications, lotions, creams or shampoos.

Treatment for secondary bacterial infections

Those with secondary bacterial infections caused due to skin abrasions caused by scratching in addition need antibiotic creams for treatment. Oral antibiotics may be prescribed if the infection is severe.

Treatment for those who have infection of the eyelashes or eyebrows

Those with infection of the eyelashes or eyebrows need to be evaluated and treated by specialists. They may develop complications like conjunctivitis, blepharitis etc.

Common myths about crabs

Common myths should be busted and patient should be counselled regarding causes of this condition and its chances of transmission. Some of these include:

  • It should be explained that pubic lice infection does not go away on its own and needs therapy. It may be passed on to others if not treated adequately.

  • In addition pubic lice infestation does not carry the risk of transmitting STIs or HIV from one person to another.

  • Condoms and other barrier contraceptives do not prevent pubic lice from spreading.

  • Getting pubic lice does not affect fertility of an individual.

  • Pubic lice infestation is not associated with getting cervical cancer (cancer of the opening of the womb called the cervix) in women.

Reviewed by , BA Hons (Cantab)

Further Reading

Last Updated: Aug 21, 2012

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