What causes blood boils on inner thigh

Overview

A boil is a painful, pus-filled bump that forms under your skin when bacteria infect and inflame one or more of your hair follicles. A carbuncle is a cluster of boils that form a connected area of infection under the skin.

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When to see a doctor
From Mayo Clinic to your inbox
Risk factors
Complications
Why do I have a bump filled with blood on my inner thigh?
Why do I keep getting blood boils?
What are blood filled boils?
How do you get rid of blood boils?

Boils (furuncles) usually start as reddish or purplish, tender bumps. The bumps quickly fill with pus, growing larger and more painful until they rupture and drain. Areas most likely to be affected are the face, back of the neck, armpits, thighs and buttocks.

You can usually care for a single boil at home. But don't attempt to prick or squeeze it — that may spread the infection.

Symptoms

Boils

Boils can occur anywhere on your skin, but appear mainly on the face, back of the neck, armpits, thighs and buttocks — hair-bearing areas where you're most likely to sweat or experience friction. Signs and symptoms of a boil usually include:

A painful, red bump that starts out small and can enlarge to more than 2 inches (5 centimeters)
Reddish or purplish, swollen skin around the bump
An increase in the size of the bump over a few days as it fills with pus
Development of a yellow-white tip that eventually ruptures and allows the pus to drain out

Carbuncles

A carbuncle is a cluster of boils that form a connected area of infection. Compared with single boils, carbuncles cause a deeper and more severe infection and are more likely to leave a scar. People who have a carbuncle often feel unwell in general and may experience a fever and chills.

When to see a doctor

You usually can care for a single, small boil yourself. But see your doctor if you have more than one boil at a time or if a boil:

Occurs on your face or affects your vision
Worsens rapidly or is extremely painful
Causes a fever
Gets bigger despite self-care
Hasn't healed in two weeks
Recurs

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Causes

Most boils are caused by Staphylococcus aureus, a type of bacterium commonly found on the skin and inside the nose. A bump forms as pus collects under the skin. Boils sometimes develop at sites where the skin has been broken by a small injury or an insect bite, which gives the bacteria easy entry.

Risk factors

Although anyone — including otherwise healthy people — can develop boils or carbuncles, the following factors can increase your risk:

Close contact with a person who has a staph infection. You're more likely to develop an infection if you live with someone who has a boil or carbuncle.
Diabetes. This disease can make it more difficult for your body to fight infection, including bacterial infections of your skin.
Other skin conditions. Because they damage your skin's protective barrier, skin problems, such as acne and eczema, make you more susceptible to boils and carbuncles.
Compromised immunity. If your immune system is weakened for any reason, you're more susceptible to boils and carbuncles.

Complications

Rarely, bacteria from a boil or carbuncle can enter your bloodstream and travel to other parts of your body. The spreading infection, commonly known as blood poisoning (sepsis), can lead to infections deep within your body, such as your heart (endocarditis) and bone (osteomyelitis).

Prevention

It's not always possible to prevent boils, especially if you have a weakened immune system. But the following measures may help you avoid staph infections:

Wash your hands regularly with mild soap. Or use an alcohol-based hand rub often. Careful hand-washing is your best defense against germs.
Keep wounds covered. Keep cuts and abrasions clean and covered with sterile, dry bandages until they heal.
Avoid sharing personal items. Don't share towels, sheets, razors, clothing, athletic equipment and other personal items. Staph infections can spread via objects, as well as from person to person. If you have a cut or sore, wash your towels and linens using detergent and hot water with added bleach, and dry them in a hot dryer.

Sept. 18, 2021

Why do I have a bump filled with blood on my inner thigh?

A painful bump or lump on the thigh can also appear red, small or large, and often be located on the inner thigh. Most commonly, bumps on the inner thigh are caused by infected ingrown hairs, boils, cysts, or a swollen lymph node. Other causes include trauma to the thigh or abnormal cell growth like lipoma.

Why do I keep getting blood boils?

The presence of the bacterium Staphylococcus aureus can cause repeat cases of boils. Once present, the body and skin may be more susceptible to reinfection. A 2015 study found that around 10 percent of people with a boil or abscess had a repeat infection within a year.

What are blood filled boils?

A blood-filled pimple is a red, swollen bump on your skin that contains blood. It can happen when you pop, squeeze, scratch or over-exfoliate a pimple, breaking the surrounding blood vessels. If you have frequent blood-filled pimples or other acne problems, talk to your primary care provider or dermatologist.

How do you get rid of blood boils?

Apply a medicated ointment (topical antibiotic) and a bandage. Continue to wash the infected area two to three times a day and to use warm compresses until the wound heals. Do not pop the boil with a needle. This could make the infection worse.