Cellulitis

What causes it and how it affects you.

What is cellulitis and what are the symptoms?

Cellulitis is a common bacterial infection of the lower layers of skin (dermis) and the subcutaneous tissues (areas underneath the skin). Cellulitis sometimes develops around wounds in the skin or surgical incisions. It usually begins as a small area of tenderness, redness and swelling. In other cases it arises without an obvious source for the bacterial infection. As the infection begins to enlarge, the person may develop a fever – sometimes with chills and sweats – and swollen lymph nodes near the infected area.

Who is at risk for cellulitis?

Anyone may develop cellulitis. However, people whose immune systems are weakened for any reason (including from chemotherapy for cancer or other immune-suppressing drugs) and those with diabetes are at highest risk for developing cellulitis.

Cellulitis may appear in areas where the skin has broken open, such as the skin near ulcers, such as those caused by athletes foot fungal problems. Surgical wounds can also create the conditions that allow the bacteria to enter the body. The infection can also occur in areas where there is no break in the skin at all, such as with chronic leg swelling (edema).

What causes cellulitis?

The majority of cases of cellulitis are caused by either staph (Staphylococcus) or strep (Streptococcus) bacteria.

Staph (Staphylococcus aureus) is the most common bacteria that causes cellulitis. There is a growing incidence of community-acquired infections due to methicillin-resistant S. aureus (MRSA), a particularly dangerous form of this bacteria that is resistant to many antibiotics and is more difficult to treat.

Strep (usually group A or B Streptococcus) is also a common cause of cellulitis. A form of rather superficial cellulitis caused by strep is called erysipelas; its conditions are characterized by spreading hot, bright red circumscribed area on the skin with a sharp raised border. Due to these factors it is sometimes referred to as the "flesh-eating bacteria" and are, in fact, also a strain of strep that can sometimes rapidly destroy tissues.

Cellulitis can be caused by many other types of bacteria.

1. In children under 6 years of age, H. flu (Hemophilus influenzae) bacteria can cause cellulitis, especially on the face, arms, and upper torso.




2. Cellulitis from a dog or cat bite or scratch may be caused by the Pasteurella multocida bacteria, which has a very short incubation period of only four to 24 hours.




3. Aeromonas hydrophilia, Vibrio vulnificus, and other bacteria are causes of cellulitis that develops after exposure to freshwater or seawater.




4. Pseudomonas aeruginosa is another type of bacteria that can cause cellulitis, typically after a puncture wound.

Is cellulitis contagious?

Cellulitis is not contagious because it is an infection of the skin’s deeper layers and the skin’s top layer provides a cover over the infection.

Where does cellulitis occur?

Cellulitis may occur anywhere on the body, but the legs and feet are the most common site of the infection, followed by the arms, and then the head and neck areas. In special circumstances, such as following surgery or trauma wounds, cellulitis can develop in the abdomen or chest areas. In cases of morbid obesity, it can also develop in the abdominal area.

How is cellulitis treated

First, it is critical for the doctor to distinguish whether or not the inflammation is due to an infection. This can be difficult at times with many cases of cellulitis because the concentration of bacteria may be low and cultures fail to show the cause of the problem.

When it proves difficult to distinguish whether or not the inflammation is due to an infection, doctors sometimes treat with antibiotics just to be sure. If the condition does not respond, it may need to be addressed by different methods dealing with types of inflammation that are not infected.

Antibiotics, such as derivatives of penicillin or other types of antibiotics that are effective against the responsible bacteria, are used to treat cellulitis. If the bacteria turn out to be resistant to the chosen antibiotics or in patients who are allergic to penicillin, other appropriate antibiotics can be substituted. In many cases, treatment requires the administration of intravenous antibiotics in a hospital setting, since oral antibiotics may not always provide sufficient penetration of the injury to be effective. In certain cases, intravenous antibiotics can be administered at home.

More on Cellulitis

Athlete’s Foot Can Lead to Cellulitis

Athlete’s foot causes cracks in the skin that allow bacteria to get under the skin and travel up to cause a cellulitis in the calf (but without an apparent infection of the foot).