Cellulitis

Definition

Cellulites (sel-u-LI-tis) is a common, potentially serious bacterial skin infection. Cellulites appears as a swollen, red area of skin that feels hot and tender, and it may spread rapidly.

Skin on lower legs is most commonly affected, though cellulites can occur anywhere on your body or face. Infections on the face are more common in children and older adults. Cellulites may affect only your skin’s surface — or, cellulites may also affect tissues underlying your skin and can spread to your lymph nodes and bloodstream.

Left untreated, the spreading infection may rapidly turn life-threatening. That’s why it’s important to seek immediate medical attention if cellulites symptoms occur.

Symptoms

Cellulitis symptoms may mean that your skin is:

  • Red
  • Swollen
  • Tender
  • Warm

The changes in your skin may be accompanied by a fever. Over time, the area of redness tends to expand. Small red spots may appear on top of the reddened skin, and less commonly, small blisters may form and burst.

Causes

Cellulitis occurs when one or more types of bacteria enter through a crack or break in your skin. The two most common types of bacteria that are causes of cellulitis are streptococcus and staphylococcus. 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 legs, especially near your shins and ankles. Disrupted areas of skin, such as where you’ve had recent surgery, cuts, puncture wounds, an ulcer, athlete’s foot or dermatitis, serve as the most likely areas for bacteria to enter.

Certain types of insect or spider bites also can transmit the bacteria that start the infection. Areas of dry, flaky skin also can be an entry point for bacteria, as can swollen skin.

Risk factors

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

  • Age. As you age, your circulatory system becomes less effective at delivering blood — with its infection-fighting white blood cells — to some areas of your body. As a result, skin abrasions may lead to infections where your circulation is poor.
  • Weakened immune system. Illnesses that result in a weakening of your immune system leave you more susceptible to infections such as cellulitis. Examples of these illnesses include chronic lymphocytic leukemia and HIV infection. Taking immune-suppressing drugs, such as prednisone or cyclosporine, also can leave you more vulnerable to infections. Immune-suppressing drugs are used to treat a variety of illnesses and to help prevent rejection in people who receive organ transplants.
  • Diabetes. Having diabetes not only increases your blood sugar level but also impairs your immune system and increases your risk of infection. Your skin is one of the many areas of your body that becomes more susceptible to infection. Diabetes may result in decreased circulation of blood to your lower extremities, potentially leading to chronic ulcers of your feet. These ulcers can serve as portals of entry for bacterial infections.
  • Chickenpox and shingles. These common viral diseases typically cause broken blisters on the skin that can serve as potential entry points for bacterial invasion and infection.
  • Chronic swelling of your arms or legs (lymphedema). Swollen tissue may crack, leaving your skin vulnerable to bacterial infection.
  • Chronic fungal infection of your feet or toes. Recurrent fungal infection of your feet or toes can cause cracks in your skin, increasing your risk of bacterial infection.
  • Intravenous drug use. People who inject illicit drugs have a higher risk of developing cellulitis.

When to seek medical advice

If you have a rash that’s red, swollen, tender and warm — and it’s expanding — try to see your doctor the same day. If a fever or pain accompanies the rash, or the rash is changing rapidly, seek emergency care. It’s important to identify and treat cellulitis early because the condition can cause a serious infection by spreading rapidly throughout your body.

Tests and diagnosis

The appearance of your skin will help your doctor make a diagnosis. Your doctor may also suggest blood tests, a wound culture or other tests to help rule out a blood clot deep in the veins of your legs. Cellulitis in the lower leg is characterized by signs and symptoms that may be similar to those of a clot occurring deep in the veins, such as warmth, pain and swelling.

Complications

This reddened skin or rash may signal a deeper, more serious infection of the inner layers of skin. Once below your skin, the bacteria can spread rapidly, entering your lymph nodes and your bloodstream and spreading throughout your body.

In rare cases, the infection can spread to the deep layer of tissue called the fascial lining. Flesh-eating strep, also called necrotizing fasciitis, is an example of a deep-layer infection. It represents an extreme emergency.

Treatments and drugs

Cellulitis treatment may involve a prescription oral antibiotic. You’ll likely recheck with your doctor one to two days after starting an antibiotic to ensure that the infection is responding to treatment. You’ll need to take the antibiotic for 10 to 14 days. In most cases, signs and symptoms of cellulitis disappear after a few days. If they don’t clear up, if they’re extensive or if you have a high fever, you may need to be hospitalized and receive antibiotics through your veins (intravenously).

Usually, doctors prescribe a drug that’s effective against both streptococci and staphylococci. An example is cephalexin (Keflex). Your doctor will choose an antibiotic based on your circumstances.

No matter what type of antibiotic your doctor prescribes, it’s important that you take the medication as directed and that you finish the entire course of medication, even if you start feeling better.