Pubic Lice (Crabs): Symptoms, Treatment & Prevention

What Are Pubic Lice?

Pubic lice (Phthirus pubis), commonly called "crabs," are tiny blood-feeding parasites that live in coarse body hair, primarily in the pubic region. They are 1-2 millimeters long, grayish-white in color, and get their nickname from their crab-like appearance with specialized claws for gripping hair shafts.

Pubic lice are a specific species of lice that have evolved to live exclusively on humans. Unlike head lice (Pediculus humanus capitis), pubic lice have specially adapted claws that are designed to grip the thicker, more widely spaced hairs found in the genital region, armpits, and other areas with coarse body hair. They cannot survive on the scalp because the hair there is too fine and closely spaced for their claws.

The life cycle of a pubic louse consists of three stages: egg (nit), nymph, and adult. Female lice lay approximately 30 eggs during their lifetime, attaching them firmly to hair shafts near the skin surface using a waterproof, glue-like substance. The eggs hatch after 6-10 days, and the emerging nymphs mature into adults within 2-3 weeks. Adult lice can live for up to 30 days while attached to a human host but will die within 24-48 hours if separated from their food source.

Pubic lice feed by biting the skin and sucking blood, typically feeding every 4-6 hours. It is this feeding behavior that causes the characteristic intense itching associated with infestation. The lice inject saliva into the skin while feeding, which contains anticoagulants and other substances that trigger an allergic reaction in most people.

Where Can Pubic Lice Be Found on the Body?

While pubic lice prefer the genital region, they can infest any area of the body with coarse hair. Common sites include:

• Pubic hair: The most common location due to ideal hair texture and warmth
• Perianal hair: Hair around the anus
• Abdominal hair: Coarse hair on the lower abdomen
• Thigh hair: Especially the inner thighs
• Armpit hair: Can spread here through body contact or migration
• Chest hair: Less common but possible in individuals with significant chest hair
• Facial hair: Including beard, mustache, and sideburns
• Eyebrows and eyelashes: More common in children who acquire lice through close contact

What Are the Symptoms of Pubic Lice?

The main symptom of pubic lice is intense itching in the affected area, which typically begins 2-4 weeks after initial infestation. Other signs include visible lice or nits (eggs) in body hair, blue-gray spots on the skin (maculae ceruleae), and dark brown specks (lice droppings) on underwear.

The symptoms of pubic lice infestation develop gradually as the body's immune system reacts to the presence of the parasites. The itching is caused by an allergic reaction to louse saliva, which is injected into the skin during feeding. This is why symptoms take 2-4 weeks to appear in first-time infestations – the body needs time to develop sensitivity to the allergens. However, if you have had pubic lice before, symptoms may appear more quickly due to existing sensitization.

The itching associated with pubic lice is characteristically intense and can be particularly bothersome at night when lice are most active. The urge to scratch can be overwhelming, but scratching can lead to secondary complications such as skin damage, bacterial infections, and increased inflammation.

Common Signs and Symptoms

Recognizing the signs of pubic lice infestation early can help you seek treatment promptly and prevent spreading the parasites to others:

• Intense itching: The hallmark symptom, often worse at night
• Visible lice: Small, grayish-white insects that move slowly through hair (may require magnification)
• Nits (eggs): Tiny, oval-shaped yellowish-white dots firmly attached to hair shafts near the base
• Maculae ceruleae: Bluish-gray spots on the skin caused by louse bites and bleeding under the skin
• Small blood spots: On underwear from louse bites
• Dark brown specks: Louse droppings visible on underwear or bedding
• Skin irritation: Redness, inflammation, and small bumps in affected areas
• Lymph node swelling: Occasionally, nearby lymph nodes may become enlarged due to the immune response

Symptoms in Different Body Areas

While the symptoms are similar regardless of location, certain areas may present unique challenges. Infestation of the eyebrows or eyelashes can cause crusting along the eyelid margins (blepharitis), eye irritation, and conjunctivitis. This presentation is more common in children and requires specialized treatment, as standard pediculicides should not be used near the eyes.

When Should You See a Doctor?

See a doctor if over-the-counter treatment doesn't work after two applications, if lice are in eyebrows or eyelashes, if you're pregnant or breastfeeding, if you develop signs of skin infection, or if you're unsure whether you have pubic lice. Most cases can be treated without medical consultation.

While pubic lice can often be treated effectively at home with over-the-counter medications, there are situations where medical advice is necessary. Healthcare providers can confirm the diagnosis, prescribe stronger medications if needed, and screen for other sexually transmitted infections that may have been acquired through the same exposure.

A medical professional can use dermoscopy (magnified skin examination) to definitively identify lice and nits, which can be helpful if you're unsure about the diagnosis. They can also distinguish pubic lice from other conditions that cause similar symptoms, such as scabies, eczema, or folliculitis.

Seek Medical Care If:

• Over-the-counter treatment fails: If lice are still alive 24 hours after proper application, or if reinfestation occurs despite following all instructions
• Lice are in eyebrows or eyelashes: Standard treatments are not safe for use near the eyes; specialized treatment is required
• You're pregnant or breastfeeding: Some treatments may not be safe during pregnancy; a doctor can recommend appropriate options
• Signs of skin infection develop: Increasing redness, warmth, swelling, pus, or fever may indicate bacterial infection
• You're unsure about the diagnosis: Other conditions can cause similar symptoms
• A child has pubic lice: May indicate inappropriate contact requiring further investigation

How Do You Get Pubic Lice?

Pubic lice are primarily spread through close body-to-body contact, especially during sexual activity. They can also spread through sharing contaminated bedding, towels, or clothing, though this is less common. Contrary to popular belief, pubic lice cannot be transmitted through toilet seats or casual contact.

Understanding how pubic lice spread is essential for both prevention and controlling infestations. The parasites require close contact to transfer between hosts because they move slowly and cannot jump or fly. Their specialized claws are adapted for gripping hair, not for moving across smooth surfaces, which limits their ability to spread through environmental contamination.

Sexual contact is by far the most common mode of transmission. During intimate contact, lice can crawl directly from one person's pubic hair to another's. This is why pubic lice are classified as a sexually transmitted infection (STI) by many health organizations, even though they don't cause disease in the traditional sense.

Primary Transmission Routes

• Sexual contact: The most common route; includes any close genital-to-genital or body-to-body contact
• Close physical contact: Extended non-sexual contact, such as sharing a bed, can also transmit lice
• Shared bedding: Lice or eggs on sheets or blankets can transfer to a new host
• Shared towels: Especially if used immediately after an infested person
• Shared clothing: Underwear, swimsuits, or other items in contact with affected areas

Myths About Transmission

Many people have misconceptions about how pubic lice spread. Understanding what doesn't transmit lice can help reduce unnecessary anxiety and stigma:

• Toilet seats: Lice cannot grip smooth surfaces and cannot survive long enough away from a host to pose a transmission risk
• Swimming pools: Lice grip tightly to hair and don't detach in water; chlorine doesn't affect their viability
• Casual contact: Handshakes, hugging, or sitting near someone with pubic lice won't spread them
• Pets: Pubic lice are species-specific and cannot live on animals

What Can You Do Yourself?

You can treat pubic lice at home using over-the-counter permethrin 1% cream rinse or pyrethrin-based products. Apply the treatment according to instructions, repeat after 7-10 days, wash all bedding and clothing in hot water (60°C/140°F), and notify sexual partners so they can be treated simultaneously.

Most cases of pubic lice can be successfully treated at home without seeing a doctor. The key to successful treatment is following the medication instructions carefully, treating all affected areas, repeating treatment to kill newly hatched lice, and taking steps to prevent reinfestation from contaminated items or untreated partners.

Before starting treatment, it's important to confirm that you actually have pubic lice. Look carefully for the parasites or their eggs using good lighting and magnification if available. Treating based on symptoms alone can delay diagnosis of other conditions that cause itching.

Step-by-Step Treatment Guide

1. Purchase an over-the-counter treatment: Look for products containing permethrin 1% or pyrethrins with piperonyl butoxide. Ask your pharmacist for help selecting an appropriate product.
2. Read all instructions carefully: Different products have different application methods and timing requirements.
3. Apply to all affected areas: This includes the pubic region, thighs, trunk, armpits, and any other areas where you've noticed lice or nits. Do not apply to eyebrows or eyelashes – see a doctor for treatment of these areas.
4. Leave on for the recommended time: For permethrin, this is typically 10 minutes. Do not exceed the recommended time.
5. Rinse thoroughly: Use warm water to completely remove the treatment.
6. Remove nits with a fine-toothed comb: While not strictly necessary for treatment success, this can reduce itching and help confirm that treatment is working.
7. Repeat treatment after 7-10 days: This second application kills any lice that may have hatched from eggs that survived the first treatment.

Environmental Decontamination

To prevent reinfestation, you must also address any lice or eggs that may be on fabrics and surfaces in your environment:

• Wash all bedding, towels, and clothing: Use hot water (60°C/140°F or higher) and dry on the highest heat setting for at least 20 minutes
• Items that can't be washed: Seal in a plastic bag for 2 weeks; lice and eggs cannot survive this long without a host
• Vacuum mattresses and upholstered furniture: While environmental transmission is uncommon, this provides additional reassurance
• Do not use fumigant sprays: These are unnecessary and may be harmful

How Are Pubic Lice Transmitted?

Pubic lice spread primarily through direct body-to-body contact, especially during sexual activity. They can also spread through sharing infected bedding, towels, or clothing. Lice cannot jump or fly and cannot survive more than 24-48 hours away from a human host.

The transmission dynamics of pubic lice are closely tied to their biology. These parasites are obligate ectoparasites, meaning they must live on the outside of a human host to survive. They have specialized claws designed to grip coarse hair and feed on human blood every 4-6 hours. Without access to a human host, they quickly dehydrate and die.

Understanding transmission helps explain why certain prevention strategies work. Since lice move slowly and cannot survive long off the body, maintaining separation between your body and potentially contaminated items, and ensuring all sexual partners are treated, effectively breaks the transmission chain.

Partner Notification

Anyone with pubic lice should inform their sexual partners from the past month so they can be examined and treated if necessary. This is essential to prevent a cycle of reinfestation between partners. If you're uncomfortable having this conversation directly, many sexual health clinics offer partner notification services that can contact partners anonymously.

How Are Pubic Lice Treated?

Pubic lice are treated with topical pediculicides, most commonly over-the-counter permethrin 1% cream or pyrethrin-based products. Treatment should be applied to all affected areas, left on for the recommended time, then rinsed off. A second application 7-10 days later is necessary to kill newly hatched lice.

Treatment for pubic lice is straightforward and highly effective when done correctly. The goal is to kill both adult lice and any eggs (nits) present, which is why two applications are typically needed – the first kills adult lice and most nits, while the second catches any lice that hatched from surviving eggs.

The most important factor in treatment success is thorough application and adherence to the treatment schedule. Partial treatment, skipping the second application, or failing to treat all affected areas can result in treatment failure and continued infestation.

First-Line Treatments (Over-the-Counter)

• Permethrin 1% cream rinse: The most commonly recommended first-line treatment. Apply to affected areas, leave on for 10 minutes, then rinse. Safe for adults and children over 2 months.
• Pyrethrin with piperonyl butoxide: Natural insecticide derived from chrysanthemums. Apply to dry hair, leave on for 10 minutes, then rinse. Avoid if allergic to ragweed or chrysanthemums.

Prescription Treatments

If over-the-counter treatments fail, healthcare providers can prescribe stronger medications:

• Malathion 0.5% lotion: Apply to dry hair, leave on for 8-12 hours, then wash off. More effective against resistant lice but has a strong odor.
• Ivermectin (oral): A single oral dose that kills lice by disrupting their nervous system. May be recommended for severe or resistant cases, or when topical treatment is impractical.
• Lindane 1% shampoo: An older treatment that is now rarely used due to potential neurotoxicity. Generally reserved for cases where other treatments have failed.

Treatment for Special Circumstances

Eyelash/eyebrow infestation: Standard pediculicides should not be used near the eyes. Treatment options include:

• Petroleum jelly (Vaseline) applied twice daily for 10 days, which suffocates the lice
• Prescription ocular-grade ointments
• Manual removal of lice and nits using fine forceps by a healthcare provider

Pregnancy and breastfeeding: Permethrin is generally considered safe during pregnancy and breastfeeding, but always consult with a healthcare provider before using any treatment. Pyrethrins are also typically considered acceptable. Lindane should be avoided.

Pubic Lice During Pregnancy and Breastfeeding

Pregnant and breastfeeding individuals can safely use permethrin 1% for pubic lice treatment after consulting with a healthcare provider. Permethrin has minimal absorption through the skin and is considered low-risk. Lindane should be avoided during pregnancy and breastfeeding.

If you discover pubic lice while pregnant or breastfeeding, it's natural to be concerned about treatment safety. The good news is that the most commonly used treatments have been studied and are considered safe when used as directed. However, it's always best to consult with your healthcare provider before using any medication during pregnancy or while breastfeeding.

Permethrin 1% cream rinse is the preferred treatment during pregnancy. Studies have shown that very little of the medication is absorbed through the skin, and the small amount that is absorbed is quickly metabolized. The World Health Organization and major medical organizations consider permethrin safe for use during pregnancy when used as directed.

Pyrethrins are also generally considered acceptable during pregnancy, though they may cause more skin irritation than permethrin. Lindane should be avoided entirely during pregnancy and breastfeeding due to potential neurotoxicity and greater systemic absorption.

How Can You Prevent Pubic Lice?

Prevent pubic lice by avoiding close contact with infected individuals, not sharing towels or bedding with others, and ensuring all sexual partners are treated if an infestation occurs. While condoms protect against many STIs, they do not prevent pubic lice transmission.

Prevention of pubic lice focuses on two main strategies: avoiding exposure to infected individuals or contaminated items, and breaking the cycle of reinfestation if you or a partner become infected. Understanding that pubic lice spread through close contact – primarily sexual – helps inform prevention strategies.

It's worth noting that pubic lice prevention differs from many other STIs because condoms do not provide protection. The lice live on pubic hair around the genital area, not on the genitals themselves, so barrier protection during intercourse doesn't prevent transmission. The most effective prevention is knowing your partner's status and avoiding contact if either person has an active infestation.

Prevention Strategies

• Limit sexual partners: Having fewer sexual partners reduces exposure risk
• Communication: Discuss sexual health openly with partners; ask about any symptoms
• Avoid sharing personal items: Don't share towels, underwear, or bedding with others
• Regular inspection: If concerned about exposure, check for lice or nits
• Prompt treatment: If infected, treat immediately and notify partners
• Complete treatment course: Finish both applications to prevent reinfestation

Preventing Reinfestation

Reinfestation is common when prevention steps are not followed carefully. To prevent recurrence:

• Treat all partners simultaneously: If only one person is treated, the untreated partner can reinfect them
• Avoid sexual contact until treatment is complete: Wait until both treatment applications are done and no live lice are present
• Decontaminate environment thoroughly: Wash all bedding, towels, and clothing in hot water
• Complete the second treatment: Do not skip the 7-10 day follow-up application