Furuncle

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Overview

A boil (furuncle) is a pus-filled bump in the skin that is caused by a bacterial infection. It’s a bit like a very big yellow pimple, but it’s deeper in the skin and hurts a lot more.


Boils develop when a hair follicle and the surrounding tissue become infected. Hair follicles consist of one hair, the root of the hair, a sebaceous gland and a small muscle that can pull the hair up, making it stand on end. Hair follicle inflammations are sometimes also referred to as “deep folliculitis” or “perifolliculitis.”


The infection causes the skin tissue inside the boil to die, creating a pus-filled hollow space (an abscess). Skin abscesses can develop from boils, but also from other things like infected insect bites or injections with dirty needles. If several boils merge into a larger bump, it’s called a carbuncle.


Sometimes boils go away again on their own, without causing any problems. But it’s often a good idea to get medical treatment. This can help make boils go away quicker, relieve the pain and prevent complications.


Symptoms

Boils are painful swollen bumps, ranging from roughly the size of a cherry stone to that of a walnut. They feel warm and look red, and yellowish pus may show through the skin. If a cluster of boils (a carbuncle) develops, the infection might cause a fever too, making you feel weak and tired.

Boils mainly occur on the face and neck, including the back of the neck. But they sometimes also develop in the armpits, groin, genital area, on the back, bottom or thighs.

Causes

Bacteria typically cause a furuncle, the most common being Staphylococcus aureus — which is why furuncles can also be called staph infections. S. aureus normally resides on some areas of the skin.

S. aureus can cause an infection in situations where there are breaks in the skin, such as a cut or a scratch. Once the bacteria invade, your immune system tries to fight them. The boil is actually the result of your white blood cells working to eliminate the bacteria.

You are more likely to develop a boil if your immune system is compromised or if you have a medical condition that slows down the healing of your wounds.

Diabetes and eczema, a chronic skin disorder characterized by extremely dry, itchy skin, are two examples of chronic conditions that may increase your risk of getting a staph infection.

Your risk can also increase if you engage in close, personal contact with someone who already has a staph infection.


Risk factors

Direct physical contact with infected individuals, primarily family members or health care personnel, is the main risk factor for development of furunculosis. Risk factors associated with recurrent furunculosis were investigated in a case control study including 74 patients with recurrent furunculosis and an equal number of patients with nonrecurrent furunculosis.4 Nasal swabs revealed S. aureus in 89% and 100% of recurrent and nonrecurrent furunculosis, respectively, and no significant differences were detected in resistance to the commonly used antibiotics. The most important independent predictor of recurrence was a positive family history. Other independent predictors were anemia, previous antibiotic therapy, diabetes mellitus, previous hospitalization, multiplicity of lesions, poor personal hygiene, and associated diseases.4 Established skin diseases such as atopic dermatitis, chronic wounds, or leg ulcers increase the susceptibility to bacterial colonization and are more prone to develop furunculosis.8 Deficiency of mannose-binding lectin as well as impaired neutrophil function in mentally retarded adults have also been associated with furunculosis.9–11 Obesity and hematological disorders are also predisposing factors. Nonetheless, in the majority of cases, no convincing predisposing factors can be incriminated.

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Complications

The majority of furuncles heal without medical intervention or complications, but in rare cases, boils can lead to more complicated and dangerous medical conditions.

Sepsis

Bacteremia is an infection of the bloodstream that may occur after having a bacterial infection, such as a furuncle. If untreated, it can lead to severe organ dysfunction such as sepsis.

MRSA

When infection is due to methicillin-resistant S. aureus, we call it MRSA. This type of bacteria can cause boils and make treatment difficult.

This infection can be very difficult to treat and requires specific antibiotics for treatment.


Prevention

Boils are painful swollen bumps, ranging from roughly the size of a cherry stone to that of a walnut. They feel warm and look red, and yellowish pus may show through the skin. If a cluster of boils (a carbuncle) develops, the infection might cause a fever too, making you feel weak and tired.

Boils mainly occur on the face and neck, including the back of the neck. But they sometimes also develop in the armpits, groin, genital area, on the back, bottom or thighs.