Cellulitis is a common, potentially serious bacterial skin infection. Cellulitis appears as a swollen, red area of skin that feels hot and tender.

It can spread rapidly to other parts of the body. Cellulitis isn't usually spread from person to person.

Skin on lower legs is most commonly affected, though cellulitis can occur anywhere on your body or face.

Cellulitis might affect only your skin's surface. Or it might also affect tissues underlying your skin and can spread to your lymph nodes and bloodstream.

Left untreated, the spreading infection can rapidly turn life-threatening. It's important to seek immediate medical attention if cellulitis symptoms occur.

 

SYMPTOMS

 

Possible signs and symptoms of cellulitis, which usually occur on one side of the body, include:

 

• Red area of skin that tends to expand

 

• Swelling

 

• Tenderness

 

• Pain

 

• Warmth

 

• Fever

 

• Red spots

 

• Blisters

 

• Skin dimpling

 

CAUSES

 

Cellulitis occurs when bacteria, most commonly streptococcus and staphylococcus, enter through a crack or break in your skin.

The incidence of a more serious staphylococcus infection called methicillin-resistant Staphylococcus aureus (MRSA) is increasing.

Although cellulitis can occur anywhere on your body, the most common location is the lower leg.

Bacteria are most likely to enter disrupted areas of skin, such as where you've had recent surgery, cuts, puncture wounds, an ulcer, athlete's foot or dermatitis.

Certain types of insect or spider bites also can transmit the bacteria that start the infection. Bacteria can also enter through areas of dry, flaky skin or swollen skin.

 

RISK FACTORS

 

Several factors can place you at greater risk of developing cellulitis:

 

Injury.

 Any cut, fracture, burn or scrape gives bacteria an entry point.

 

Weakened immune system.

 Conditions that weaken your immune system — such as diabetes, leukemia and HIV/AIDS — leave you more susceptible to infections.

Certain medications, such as corticosteroids, also can weaken your immune system.

 

Skin conditions. 

Skin disorders — such as eczema, athlete's foot, chickenpox and shingles — can cause breaks in the skin and give bacteria an entry point.

Chronic swelling of your arms or legs (lymphedema). Swollen tissue may crack, leaving your skin vulnerable to bacterial infection.

 

History of cellulitis. 

People who previously had cellulitis, especially of the lower leg, may be more prone to develop it again.

 

Intravenous drug use.

 People who inject illegal drugs have a higher risk of developing cellulitis.

 

Obesity.

 Being overweight or obese increases your risk of developing cellulitis and having recurring episodes.

 

TESTS AND DIAGNOSIS

 

Your skin's appearance will help the doctor make a diagnosis. He or she may also suggest blood tests, a wound culture or other tests to help rule out other conditions.

 

TREATMENTS AND DRUGS

 

Cellulitis treatment usually includes a prescription oral antibiotic. Within three days of starting an antibiotic, let the doctor know whether the infection is responding to treatment.

Patients need to take the antibiotic for as long as the doctor directs, usually 5 to 10 days but possibly as long as 14 days.

In most cases, signs and symptoms of cellulitis disappear after a few days. One may need to be hospitalized and receives antibiotics through the veins (intravenously) if:

 

• Signs and symptoms don't respond to oral antibiotics

 

• Signs and symptoms are extensive

 

• You have a high fever

 

Usually, doctors prescribe a drug that's effective against both streptococci and staphylococci. It's important that one takes the medication as directed and finishes the entire course of medication, even after you feel better.

The doctor also might recommend elevating the affected area, which may speed recovery.

 

COMPLICATIONS

 

The bacteria that cause cellulitis can spread rapidly, entering lymph nodes and the bloodstream. 

Recurrent episodes of cellulitis may damage the lymphatic drainage system and cause chronic swelling of the affected limb.

In rare cases, the infection can spread to the deep layer of tissue called the fascial lining.

 Flesh-eating strep (necrotizing fasciit

is) is an example of a deep-layer infection. It represents an extreme emergency.