What are crabs?

You'll know you have crabs if you see a louse or lice, are itchy, or see spots of blood or black lice feces in your pubic area.
You'll know you have crabs if you see a louse or lice, are itchy, or see spots of blood or black lice feces in your pubic area.

Pubic lice, often called crabs, are a type of small insect that prefers to live in the coarse hair found in the pubic area. They can also live elsewhere, including the armpits, chest, or facial hair. Crabs are not a disease: they are a common parasite that infects millions of people each year.

Pubic lice are small, less than 2 millimeters long. While they are visible to the eye, they may not be noticed immediately in coarse hair. They feed on blood, biting the skin to eat. The entire life cycle of a pubic louse occurs on the human body, including laying eggs, so it’s not uncommon to find egg sacs in pubic hair along with the lice themselves.

Having pubic lice can be uncomfortable and unpleasant. Recognizing the signs and symptoms of public lice can help you identify when you should get treated.

Signs and symptoms of crabs

The most common sign of having crabs is seeing a louse in your pubic area. While you may have just one louse, it is more common to have multiple. If you see one, there are likely more, and you have been infected with pubic lice.

Other warning signs of crabs include:

Itchy pubic area

One of the most frequent symptoms of crabs, outside of seeing the lice, is feeling itchy from their bites. You may also be able to feel them moving, which can also make you itchy. This itch will often be its worst at night.

Inflammation and irritation

If your pubic area is itchy, you’re likely to scratch it. That can lead to irritation and inflammation of the delicate skin in the area. You may also experience swelling or irritation as a result of an allergic reaction to the lice bites.

Spots of blood

When lice bite you, they may leave small spots of blood or blue dots on your skin. These spots can be found on your thighs, pubic area, and lower abdomen, or anywhere else that pubic lice inhabit.

Black powder in clothing

Since public lice are insects, they excrete just like any other insect. If you have a significant infestation of pubic lice, you may start to notice black powder in your underwear and clothes. This is the pubic lice’s feces.

Causes of crabs

Because of their location, pubic lice are frequently transmitted through sexual contact. It’s easy for the lice or egg sacs to transfer from one person to another during sexual activity. However, there are several other ways you can get crabs without being sexually active.

Other potential causes of pubic lice include:

Sharing clothing

Sharing clothing, especially pants or intimate apparel, can transfer crabs from one person to another. The egg sacs and lice can hold onto fabric just as easily as they can hold onto hair, so unwashed clothing can easily transmit the parasites.

Sharing towels

As with clothing, sharing towels can spread pubic lice egg sacs from one person to another. Towels can also transfer pubic lice to other parts of the body, such as the armpits or facial hair.

Sharing beds

Finally, sharing a bed or using a bed that someone with pubic lice has slept in can sometimes give you a pubic lice infection. Public lice seek out heat, so if they are in the bedding, they may migrate onto your body.

Diagnosing crabs

Your doctor can easily diagnose you if you have crabs. To identify pubic lice, your doctor will first ask you questions about your symptoms to rule out other problems. Then a healthcare professional will examine your pubic area or anywhere else that you feel may be infested.

They will look for signs of live lice, egg sacs, and juvenile lice known as mites. If they see any of these problems, they will confirm that you have pubic lice and direct you to appropriate treatment.

Treatments for crabs

Since crabs are insects, they cannot be treated like other STIs. Instead, it’s necessary to use treatments that can kill bugs. Commonly, this includes using over-the-counter lice-killing lotions, mousses, or shampoos. In many cases, a course of a 1% permethrin lotion can completely resolve a case of pubic lice.

Make sure you complete the treatment and follow the instructions carefully, since many treatments for pubic lice can be toxic to humans if ingested. In rare cases, you may need to reach out to your doctor for an oral prescription if over-the-counter treatments aren’t effective.

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Medically Reviewed on 12/14/2020
References
American Sexual Health Association: "Pubic Live: Fast Facts."

Avert: "Pubic Lice Symptoms and Treatment."

Centers for Disease Control and Prevention: "About Pubic “Crab” Lice."

Centers for Disease Control and Prevention: "Pubic Lice Treatment."

National Health Service: "Pubic lice."