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Cellulitis is a common bacterial skin infection caused by bacteria known as group A Streptococcus (group A strep) and Staphylococcus aureus (S. aureus). These bacteria are typically found on the skin and in the nose and throat of healthy individuals.

Although cellulitis is not contagious, it can affect anyone. Certain skin injuries (cuts, burns, piercings, insect bites) and skin conditions, such as shingles (a viral skin condition), eczema (an allergic skin condition), or athlete's foot (a fungal skin infection), allow bacteria to enter the skin, thus increasing your risk of developing cellulitis.

Many people develop cellulitis when bacteria enter the skin through lacerations (deep cuts or tears in the skin) or surgical wounds. This allows cellulitis to develop anywhere in the body, but it typically affects the arms and legs.

This article discusses the transmission, risk factors, and treatments of cellulitis.

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The severity of your cellulitis depends on the types of bacteria involved, the location of your infection, how deep it's in your skin, and if it has become widespread.

Researchers believe that group A strep and S. aureus are the primary bacteria that cause cellulitis.

Both types of bacteria are commonly found on the skin or in the nose and throat of healthy individuals. However, they can become pathogenic (disease-causing) under the right conditions—such as a deep skin injury or a skin condition.

Cellulitis can also be caused by bacteria, such as Pasteurella  and Capnocytophaga, that enter the skin through animal bites and scratches. You can also develop cellulitis if your injured skin is exposed to bacteria that live in saltwater (Vibrio vulnificus ) or freshwater (Aeromonas ).

Although cellulitis can develop anywhere on the body, it typically affects the arms and legs where the skin is prone to injury. Cellulitis affects the deeper layers of the skin. These include the dermis (middle layer of skin) and subcutaneous (innermost layer of the skin that contains connective tissue and nerves) layers.

Cellulitis is not contagious (spread from person to person). However, the infection can reach deeper layers of the skin or spread rapidly in the bloodstream if left untreated. If you have an underlying health condition or are immunocompromised (have a weakened immune system), you are more likely to develop serious complications.

Many cases of cellulitis are mild and can be treated with medications. Common symptoms of cellulitis include:

In some cases, cellulitis can become systemic (widespread in the body) and lead to severe infection. Seek immediate medical attention if you experience any of these symptoms:

If you have diabetes, are immunocompromised, or have untreated cellulitis, serious and potentially fatal complications can occur. These include sepsis (a whole-body reaction to bacteria in the bloodstream), necrotizing fasciitis (rare infection that destroys soft tissue and muscles), and abscess (walled-off collection of pus).

Seek immediate medical attention if your condition does not improve or you have any concerning symptoms.

Although anyone can develop cellulitis, risk factors that increase your chances of infection include:

Cellulitis is commonly treated with antibiotics, which are a group of medications that kill or prevent the growth of bacteria. The type of antibiotics you'll receive from your healthcare provider depends on the type of bacteria that is associated with your cellulitis and the severity of your infection. Antibiotics may be taken orally (by mouth) or intravenously (inserted into a vein).

For most cellulitis cases, the Centers for Disease Control and Prevention (CDC) recommends that patients receive a five-day course of antibiotic treatment. However, the exact duration will depend on the severity of the infection. In most people, symptoms of cellulitis should improve within 24 to 48 hours of starting antibiotic treatment.

Antibiotic-resistant strains of staph bacteria, commonly known as methicillin-resistant Staphylococcus aureus (MRSA), are resistant to many antibiotics, including methicillin, amoxicillin, and penicillin. MRSA can be acquired through the community (C-MRSA) or in the hospital (HA-MRSA).

For superficial (surface of skin) infections caused by MRSA, your healthcare provider will drain the abscess. If your infection is deeper in the skin, only a handful of antibiotics are effective against MRSA. These include vancomycin, daptomycin, and linezolid.

Many MRSA infections are picked up during hospital stays. For this reason, it's very important for healthcare providers and people to thoroughly wash their hands and keep surfaces and rooms clean. MRSA is easily transmitted from person to person through contaminated medical devices, handles, doorknobs, and more.

To determine if your cellulitis is improving or getting worse, it can be helpful to draw a circle around the infected area. Observe the redness within the circled area and note the following:

In addition to taking antibiotics, consider elevating your arm or leg to reduce swelling and inflammation. You may also want to apply a cool compress to alleviate pain and discomfort and get plenty of rest.

Recurrent cellulitis is common. Studies show that about 22% to 49% of people with cellulitis have been infected at least once before.

To prevent recurring cellulitis, keep your skin clean and hydrated. If you have eczema or athlete's foot, take any prescribed medicines as instructed by your healthcare provider. Your healthcare provider may also recommend long-term antibiotic treatment if you are in a higher risk group or develop cellulitis frequently.

Cellulitis is a common bacterial skin infection caused by group A Streptococcus (group A strep) and Staphylococcus aureus (S. aureus). These bacteria are typically found on the skin and in the nose and throat of healthy individuals.

Cellulitis is not contagious, but it can affect anyone. Certain skin injuries and skin conditions allow bacteria to enter the skin and increase your risk of developing cellulitis. Cellulitis typically affects the arms and legs.

Common symptoms of cellulitis include redness and swelling of the skin, tenderness, blisters, headaches, and more. If you have an underlying disease or are immunocompromised, you are at greater risk of developing serious complications, including sepsis and necrotizing fasciitis.

To treat cellulitis, antibiotics are most commonly prescribed by healthcare providers. The type of antibiotics and the exact dosage will depend on the type of bacteria associated with your cellulitis and which antibiotics are most likely to be effective.

Although most cases of cellulitis are mild, do not ignore the signs and symptoms of cellulitis. This is especially true if you have diabetes or are immunocompromised, which puts you at a greater risk for developing serious to life-threatening complications. Early detection allows for more effective treatments.

To prevent cellulitis, wash your hands regularly and hydrate your skin afterward. Also, consider wearing long-sleeved clothing to protect skin from injuries, such as minor cuts and tears, and deep lacerations.

As a good rule of thumb, monitor and observe potential changes in your symptoms. A persistent rash or deepening redness may indicate a worsening infection. Seek immediate medical attention if this occurs.

The type of antibiotics you'll receive from your healthcare provider depends on the type of bacteria associated with your cellulitis and the severity of your infection. Refer to the Johns Hopkins ABX guide for a list of commonly used antibiotics.

Practicing good hygiene, such as bathing and hand washing, can minimize your chances of being infected with cellulitis. However, make sure to hydrate your skin with a moisturizer after bathing and hand washing. Moisturizing your skin can prevent dry, itchy skin and skin cracks that bacteria can enter through.

To know if your cellulitis is healing, look for signs of improvement in the infected area. This includes a smaller rash, reduced pain, and a decrease in swelling, warmth, and redness.

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