What is Bacterial Cellulitis?

A.E. Freeman

Bacterial cellulitis is an infection of the skin commonly caused by certain types of Streptococcus bacteria. Staphylococcus bacteria is perhaps the most common cause of bacterial cellulitis. The methods by which a person can get the infection vary widely. Some people may get infected from an open wound, such as an animal bite, while others may have cellulitis in a swollen area of the skin that has not been broken.

Cellulitis may occur from a spider bite.
Cellulitis may occur from a spider bite.

Bacterial cellulitis usually develops on the skin of a person's legs, particularly in the area of the calf or ankle. It can develop on other parts of a person's body as well, such as the face, neck, and arms. Some obese people may also get bacterial cellulitis on the skin of their abdomen.

Bacterial cellulitis may require intravenous antibiotics.
Bacterial cellulitis may require intravenous antibiotics.

An infection usually appears as a red rash on the affected area. The rash is typically painful and feels tender to the touch. As the infection continues, the skin becomes warm to the touch and will swell. Blisters of varying sizes may form in the affected area, and a person may develop a fever as well.

Bacterial cellulitis tends to infect the deeper tissues of the skin, such as the dermis and subcutaneous tissue. If it is not treated quickly enough, the infection can spread to a person's lymph nodes, causing them to swell and feel painful, and to the bloodstream. Once in the bloodstream, the infection can spread throughout the body, which can be particularly risky.

People who have compromised immune systems, such as those who have HIV/AIDS or who are undergoing chemotherapy, have a greater risk of infection. A person prone to skin problems such as eczema is also more prone to bacterial cellulitis, as are people who use intravenous drugs or who suffer from chronic edema, or swellig. Fortunately, bacterial cellulitis is not contagious, as it is in the lower layers of the skin.

The infection can usually be treated and cleared up with a course of antibiotics. Ideally, the antibiotics will be taken by mouth for about two weeks. They should be designed to fight against both streptococcus and staphylococcus bacteria. Penicillin is a common antibiotic, but may not be used in some cases, such as if the patient is allergic. Generally, a patient should check in with her doctor after taking the medication for a few days to make sure it is working. If the cellulitis is severe and spreading, a person may need to receive the antibiotics intravenously instead of orally.

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Discussion Comments


My grandmother, who is a diabetic, was hospitalized with cellulitis once. People with diabetes need to be extra careful because diabetes damages blood circulation which can reduce feeling in the legs and feet. Elderly diabetics may not feel and notice injuries to the legs and feet for this reason.

This is what happened to my grandmother. The cut on her leg turned into cellulitis before she even realized what was going on. Thankfully, she responded very well to the antibiotics.


@SarahGen-- It's true that bacteria need to enter the lower layers of skin to cause cellulitis and it certainly does that through an opening. But the opening may be so small that you may not notice it. So there doesn't necessarily need to be a visible cut or opening on skin that has cellulitis.

Sometimes, the bacteria causing cellulitis are bacteria that normally live on top of skin without causing any problems. These bacteria can even be part of the natural skin flora. But when they enter into the lower layers, they can suddenly lead to an infection. This makes cellulitis difficult to prevent in some cases. That's why a doctor must be seen as soon as the symptoms show up.

How does cellulitis occur in an area of skin that's not broken? Doesn't the bacteria need to enter from somewhere?
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