Pubic Lice Crabs: Symptoms, Types, Causes and Treatment

Pubic lice, commonly known as "crabs," are tiny parasitic insects that have plagued humans for thousands of years. Despite their small size, these ectoparasites can cause significant discomfort and social stigma. Understanding the symptoms, types, causes, and treatment options is key to recognizing and managing infestations promptly and effectively. This article synthesizes the latest clinical and scientific insights to offer a detailed, human-centered guide to pubic lice crabs.

Symptoms of Pubic Lice Crabs

Recognizing the symptoms of pubic lice is crucial for early detection and effective treatment. While the primary sign is itching, these parasites can cause a range of physical and visible symptoms. Symptoms may vary depending on the area of infestation and the severity, but they are almost always bothersome.

Symptom	Description	Common Sites	Source(s)
Itching	Persistent, often intense pruritus	Pubic region, body	1 6
Red Papules	Small red bumps caused by bites	Pubic area, thighs	1 6
Rust/Brown Stains	Discolored deposits from lice feces or blood	Underwear, skin	1
Visible Lice/Nits	Tiny, whitish eggs (nits) or adult lice attached	Hair (pubic, eyelashes, body)	1 3 4 6

Table 1: Key Symptoms

Common Physical Symptoms

Itching is the hallmark symptom of pubic lice infestation. This itching, or pruritus, is caused by an allergic reaction to louse saliva injected during feeding. The discomfort may intensify at night or after hot showers, often disturbing sleep and quality of life 1 6.

Visible Signs

Red papules, or small bumps, may develop in the infested region due to repeated bites. Some people also notice bluish spots or rust- or brown-colored stains on their skin or underwear, which are deposits from lice feeding or their fecal matter 1.

Where Lice Are Found

Although pubic lice prefer the coarse hair of the pubic region, they can also infest other areas:

• Body hair (including chest, abdomen, armpits)
• Beard and mustache
• Eyelashes (phthiriasis palpebrarum), particularly in children
• Eyebrows
• Rarely, scalp hair—especially in severe cases or in children 1 2 3 4

Nits and Adult Lice

Nits—tiny, oval, whitish eggs—are firmly attached to the base of hair shafts and are often easier to spot than adult lice. Adult lice are small (about 1–2 mm), grayish, and crab-like in appearance but can be difficult to see without magnification 1 3.

Less Common Symptoms

• Mild fever or malaise (rare)
• Eye irritation and redness (if eyelashes are involved) 3 4

Types of Pubic Lice Crabs

While the term "pubic lice" usually refers to one species, it's important to distinguish between the three main types of lice that infest humans and to recognize the varied sites Pthirus pubis can affect.

Louse Type	Scientific Name	Preferred Location	Source(s)
Head Louse	Pediculus humanus capitis	Scalp hair	2
Body Louse	Pediculus humanus corporis	Clothing seams, body hair	2
Pubic Louse	Pthirus pubis	Pubic, body, facial hair, eyelashes	1 2 3 4

Table 2: Louse Types and Locations

Pthirus pubis: The Crab Louse

Pthirus pubis is uniquely adapted to live in coarse, widely-spaced hair, giving it the classic "crab" appearance under the microscope. Unlike head or body lice, pubic lice have a broader body and strong claws for gripping pubic hair 1 2.

Non-Pubic Locations

• Eyelashes/Eyebrows: When pubic lice infest the eyelashes (phthiriasis palpebrarum), it's more common in children and may signal child abuse 3 4.
• Body and Facial Hair: Pubic lice can also be found in armpit hair, chest hair, beard, or mustache, especially in cases of heavy infestation 1 3.
• Scalp Hair: Rare, but possible, especially in children or in association with eyelash involvement 2 3.

Morphological Differences

• Crab lice (Pthirus pubis): Short, broad, and crab-shaped body, specialized for clinging to coarse hair 2.
• Head/body lice (Pediculus species): Elongated bodies adapted to finer hair or clothing seams.

Causes of Pubic Lice Crabs

Understanding how pubic lice are transmitted and what risk factors contribute can help reduce the chances of infestation and guide public health prevention strategies.

Cause	Description	Risk Factor	Source(s)
Close Contact	Skin-to-skin, especially sexual contact	Multiple partners, sexual activity	1 5
Infested Items	Rare, but via contaminated towels, bedding	Shared use	1
Overcrowding	Increased lice spread in close quarters	Institutions, war, disasters	1
Reduced Grooming	Less pubic hair removal increases risk	Personal hygiene habits	1

Table 3: Transmission and Risk Factors

Primary Transmission Route

The vast majority of pubic lice cases are transmitted by direct, close body contact—most commonly during sexual activity. This is why the lice are often considered a sexually transmitted infestation 1 5. However, sexual activity is not the only risk factor.

Non-Sexual Transmission

Though less common, pubic lice can be spread through contact with contaminated towels, bedding, or clothing. Lice cannot jump or fly; they crawl from hair to hair or via infested items 1. Such transmission is more likely in crowded living conditions, such as during wars or natural disasters 1.

Risk Factors

• Sexual activity: Especially with multiple partners
• Overcrowding: Living in close quarters (e.g., shelters, prisons)
• Shared personal items: Towels, bedding, or clothing
• Reduced pubic hair grooming: Modern grooming trends (e.g., waxing or shaving) have reduced the incidence of pubic lice in some populations, as lice lose habitat 1.

Special Considerations

• Children: Eyelash or eyebrow infestation may suggest close contact with an infested adult and, in rare cases, can be an indicator of abuse 3.
• Other Infections: Pubic lice infestation should prompt screening for other sexually transmitted infections (STIs) as coinfection is possible 5.

Treatment of Pubic Lice Crabs

Effective treatment of pubic lice involves both eliminating the parasites and preventing reinfestation. Multiple therapies are available, and treatment should be tailored to the area affected, patient age, and potential resistance.

Treatment	Description	Application Area	Source(s)
Permethrin	Topical cream or shampoo, first-line therapy	Pubic/body/eyelashes	1 4 6
Pyrethrins	Plant-based insecticide, alternative first-line	Pubic/body hair	1 5
Mechanical Removal	Manual removal with forceps/combs	Eyelashes, small areas	1 3 4
Petrolatum Jelly	Smothers lice, especially on eyelashes	Eyelids/eyelashes	4
Alternative Agents	Malathion, Ivermectin, Phenothrin	Resistant cases	1

Table 4: Treatment Options

First-Line Treatments

• Permethrin 1% cream or shampoo: Apply to the affected area, leave for 10 minutes, then rinse off. Repeat after 7–10 days to catch newly hatched lice 1 4 6.
• Pyrethrin-based products: Also effective, but ensure not to use products containing piperonyl butoxide for eyelid infestations 1 5.

Alternative and Second-Line Treatments

• Malathion, Ivermectin, Phenothrin: Used when resistance or intolerance to first-line agents is suspected. These may require a prescription and supervision 1.
• Petrolatum jelly (Vaseline): Effective for eyelashes, applied carefully to smother lice and nits. Avoid getting into the eyes 4.
• Manual removal: Using fine forceps to remove lice and nits from eyelashes or small areas. This is often combined with other topical treatments 3 4.

Special Situations

Eyelash and Eyebrow Infestations

• Do not use regular insecticidal creams or shampoos near the eyes.
• Petrolatum jelly can be safely applied to eyelashes several times daily for 7–10 days 4.
• Manual removal with forceps and slit-lamp examination may be necessary for stubborn cases 3 4.
• Fluorescein eye drops: Experimental use showed some effectiveness in killing lice on eyelashes, but clinical data are limited 3.

Treating Contacts and Preventing Reinfection

• Treat all sexual partners and close contacts simultaneously to prevent reinfestation 1 5.
• Wash clothing, bedding, and towels in hot water and dry on high heat.
• Avoid sexual contact and close physical contact until treatment is complete and follow-up confirms eradication 1 5 6.

Resistance and Pseudoresistance

• Resistance to insecticides is well-documented in head lice and presumed possible in pubic lice. If a treatment fails, ensure correct application, repeat the course, and consider switching to a different class of medication 1.
• Pseudoresistance—failure due to improper use or reinfestation—should be excluded before changing therapies 1.

Medical Review and STI Screening

Because pubic lice are frequently associated with risk factors for sexually transmitted infections, screening for other STIs is recommended as part of the management plan 5.

Conclusion

Pubic lice, or crabs, remain a persistent, though declining, human parasite. Recognizing their symptoms, understanding the different types, knowing how they spread, and using effective treatment strategies are vital for prompt management and preventing recurrence.

Key Points:

• Pubic lice cause intense itching, visible lice/nits, and skin changes, and can affect areas beyond the pubic region 1 2 3 4 6.
• Pthirus pubis is the species responsible, but can infest various body sites, including eyelashes and body hair 1 2 3 4.
• Transmission occurs mainly via close body contact, especially sexual, but also through infested items and in overcrowded conditions 1 5.
• First-line treatments include permethrin and pyrethrin-based products, with alternative options available for resistant cases. Eyelash infestations require special care 1 3 4 6.
• Treat contacts, wash personal items, and screen for other STIs to prevent reinfestation and complications 1 5 6.

With effective therapies and careful hygiene, pubic lice infestations can be quickly controlled and eradicated. If you suspect you have pubic lice, seek medical advice for diagnosis and the best treatment plan for your situation.