Pubic lice (Phthirus pubis or crab louse) is a parasitic infestation known as Pediculosis. These are tiny insects that live on coarse human hairs, preferably pubic hairs. Pubic lice survive on human blood and cannot stay alive for more than 72 hours without being on their host.
However, it is commonly transmitted by sexual contact.
What do Pubic lice look like?
Public lice are very tiny yellowish-grey and red coloured insects (up to 2 mm long), which are difficult to observe and may look like small flakes to the naked eye. They have six tiny legs, and out of them, the first two larger ones look like the claws of crabs (giving them a name as a crab).
These appendages help them to hold the base of the hairs.Pubic lice lay eggs on the hair shaft in pale brownish sacs (nits) that grips the hairs quite tightly.
The eggs(nit) hatch within five to ten days, where empty sacs take a white colour. You might find it hard to see pubic lice, but they get visible on coarse hairs on the body (except scalp hairs).
Where can Pubic lice be found?
Public lice can be found on most parts of the body, including:
- Leg hairs
- Underneath the arms
- Chest hairs
- Hairs on abdomen and back
- Moustache and beard
- Eyebrows and eyelashes (but very rare)
- However, pubic lice are not found in scalp hairs
It can take from days to weeks for symptoms to appear.
In men and women, the main symptom of Pubic lice is itching. This can get worse at night as Pubic lice is most active then. This itching is due to the allergic skin reaction to the saliva from the lice’s bite.
Other symptoms include:
- Low-grade fever
- Discomfort and inflammation secondary to excessive scratching
- Black powder in your underpants
- Blueish or red spots of blood in the affected area due to lice bites
- Sometimes, you might see lice, nits and droppings(as white or grey dots), or your partner notices them. However, it is tricky to see lice as they do not move in the light.
- Sometimes, lice and nits are accidentally noticed by the doctors during routine pelvic or a medical examination.
Can Pubic lice make me infertile?
No, pubic lice cannot affect your fertility.
How can I get Pubic lice?
Pubic lice is most commonly transmitted via:
- Close bodily contact or sexual contact with the infected person
- Sharing towels, clothes, and blankets used by the infected person
It’s transmission is not related to poor hygiene.
However, pubic lice require a human host for food (blood) and survival. It cannot survive after leaving the body unless it gets on another human body by close body contact. It cannot jump or fly but crawls hair to hair, which is enough for a human to human transmission.
Can condoms prevent me from getting Pubic lice?
Condoms or any barrier contraception do not completely protect against Pubic lice as the condom does not cover the pubic area (much like with Genital warts).
Can poor hygiene cause me Pubic lice?
Poor hygiene does not cause pubic lice. It is transmitted through sexual contact or sharing towels, beddings and clothes with an infected person.
Can I get pubic lice from oral or anal sex?
- Have protected vaginal, oral and anal sex
- Use a condom, femidom and/or dental dam with a new partner
- Only use sex toys that you know are clean
- You and your new partner get tested before having sex
- Don’t have sex with your partner if they were treated for Chlamydia less than 7 days ago
How are Pubic lice diagnosed?
Like with many skin conditions, Pubic lice is diagnosed from a physical examination. A magnifying glass may be used to better visualise the lice or nits.
If any lice or nits are found, this can be sent off for a microscope examination, further confirming the diagnosis.
In the event of finding Pubic lice, it is routinely recommended to be tested for STIs.
What factors can help a correct diagnosis?
Seeing the Pubic lice moving helps aid a correct diagnosis.
What other conditions can cause similar symptoms as pubic lice?
The following skin conditions could have similar symptoms as that of pubic lice:
- Fungal groin infection (Tinea cruris)
- Seborrhoeic dermatitis
What does it mean for me and my partner?
You can transmit Pubic lice to your sexual partner (and vice-versa).
Therefore, you must take treatment along with your sexual partner (or to whom you came in sexual contact in the last 3 months) for complete eradication of pubic lice and avoid reoccurrence.
What is the treatment for Pubic lice?
Pubic lice can be treated using topical medications (a medication which is applied directly over parts of the body).
Lifestyle changes may also be recommended to prevent reinfection and transmitting the infection to others.
- Keep the affected areas clean and dry
- Regular changing of the underpants and clothes
- Over-the-counter topical medications to treat the area
- A few stubborn lice and nits might remain in the hairs after treatment. In this case, remove them with a tweezer or special nit comb, which you can buy from a pharmacy
- Those who have come into close contact with you may also require treatment
Additionally, the following are recommended to avoid spreading the Pubic lice:
- Washing your clothes, beddings and towels at a high temperature
- Drying your clothes with an iron
- Dry cleaning items that cannot be washed
- Vacuum carpets and rugs where you think lice may have fallen
- Fumigating your house is not necessary
You may need to reapply the medicine after three to seven days of the first treatment to get rid of the remaining lice or newly hatched lice during that time.
Do I need to shave my pubic hair?
It is not necessary to shave your pubic hair.
How long does it take for the symptoms to resolve?
If you use the medication as per given instructions, the symptoms will be relieved soon. However, itching might continue for a few days after successful treatment.
How long do I have to wait until having sex?
You must wait until your partner is also treated and re-evaluated for re-infestation.
What if over the counter treatment does not work on me?
In such an event, we recommend visiting your GP or Sexual Health Clinic for further investigations and treatment.
Will my Pubic lice go away without taking any treatment?
It is unlikely that you get rid of Pubic lice without any treatment.
In fact, receiving no treatment may increase the likelihood of transmitting Pubic lice onto others. Furthermore, excessive scratching due to the itching can cause secondary infections, leave your skin scaly and even scarring.
Page reviewed by Dr. Manoj Malu (Clinical Director)
Last reviewed date: 26 April 2021
Next review due: 26 April 2024
Whilst this content is written and reviewed by sexual health specialists, it is for general guidance only. It is not intended to replace the advice of your clinician.
References & Further Reading
- NHS: Pubic lice
- CDC: Pubic “Crab” Lice
- Clinical and Experimental Dermatology: A clinical review and history of pubic lice
- Primary Care Update for OB/GYNS: The diagnosis and treatment of scabies and pubic lice