What is Cellulitis: Symptoms, Causes, Diagnosis, Treatment, and Prevention

Cellulitis can develop anywhere on the body, but in adults it most commonly affects the skin of the lower legs. In children, cellulitis often affects the face and neck, according to the American Academy of Dermatology (AAD). (1)

About 14.5 million people in the United States develop cellulitis each year.

“Cellulitis literally refers to inflammation of the skin,” says Tsippora Shainhouse, MD, a board-certified dermatologist and a clinical instructor at the University of Southern California in Los Angeles.

“It usually appears in the skin as an expanding pink or red patch that feels warm and hard, and sometimes tender to touch,” says Dr. Shainhouse.

Cellulitis can start with any break in the skin, including a minor scratch or insect bite that allows bacteria to penetrate to the deeper layers of skin. It’s rare in healthy young adults. Cellulitis is more common among elderly people and in people with weakened immune systems, chronic skin conditions that cause breaks in the skin, chronically high blood sugar levels, or obesity.

Systemic antibiotics — oral antibiotics or, in severe cases, intravenous antibiotics — are needed to treat cellulitis. Because cellulitis affects the deeper layers of skin and tissue, topical antibiotic ointments are not effective at treating cellulitis.

Cellulitis that goes untreated can spread to the lymph nodes and the bloodstream and quickly become life-threatening.

Given the serious nature of cellulitis, it’s important to seek medical care if you develop symptoms of the condition — even if you’re not sure that’s what you have.

Cellulitis Signs and Symptoms

Cellulitis can develop quickly and can lead to serious consequences, so it’s important to seek medical treatment quickly if you see signs or have symptoms of this type of infection, says the AAD. (2)

As mentioned previously, cellulitis most often occurs in the legs in adults and, according to Shainhouse, it typically occurs in one leg at a time, not both at once.

Common symptoms of cellulitis include:

  • Skin redness
  • Swelling
  • Pain or tenderness
  • Skin that’s warm to the touch
  • Fever
  • Red spots
  • Skin dimpling

You may not notice warmth or pain until you touch or press an area affected by the infection. Some people develop other symptoms before there’s a change in the appearance of their skin, such as chills or fatigue, notes the AAD. (3)

Causes and Risk Factors for Cellulitis

“Cellulitis is usually caused by a variety of bacteria, most predominantly staphylococcus ('staph') and streptococcal ('strep') species that live on the skin. These bacteria invade below the skin through abrasions and cuts, and infect the tissues beneath the skin, causing an inflammatory response,” says Amesh A. Adalja, MD, a board-certified infectious disease physician in Pittsburgh and a senior scholar at the Johns Hopkins University Center for Health Security.

While staph and strep can live harmlessly on your intact skin, any type of open sore on your body — including a burn, a surgical wound, or even a pimple — can allow the bacteria in and put you at risk of developing cellulitis, says Shainhouse.

Of course, many people sustain many minor skin wounds over the course of their lives and never develop cellulitis. But certain conditions place people at increased risk for cellulitis. Such conditions include:

  • Advanced age, which is associated with a weaker immune system
  • A disease that weakens the immune system, such as an autoimmune disease, diabetes, cancer, and HIV or AIDS
  • Use of a medication that suppresses the immune system (2)
  • Injection of illicit drugs
  • Impaired lymphatic drainage (4)
  • Obesity or being overweight

There’s also the risk of cellulitis if you have a skin condition like eczema or athlete’s foot that can cause dryness and itchiness and breaks in the skin, providing an entry point for bacteria.

Having had cellulitis once also puts you at higher risk of developing it again, according to the Mayo Clinic. (5)

How Cellulitis Is Diagnosed

A doctor can often diagnose cellulitis simply by examining the skin, although blood tests and a blood culture may be used to confirm a diagnosis, notes the Mayo Clinic. (6)

“Some common mimickers of cellulitis include venous stasis dermatitis, contact dermatitis, eczema, an insect bite reaction, shingles, deep vein thrombosis (DVT), vein inflammation, and gout,” says Shainhouse.

It’s also important to rule out necrotizing fasciitis, a bacterial infection that can quickly destroy the tissue beneath the layers of skin. This is the condition commonly referred to as “flesh-eating disease.”

Conditions That May Be Confused With Cellulitis

Gout Symptoms and Diagnosis

Here’s a closer look at a few skin conditions that could be mistaken for cellulitis, per VisualDx: (7)

Venous Stasis Dermatitis This type of redness and swelling of the lower legs is due to poor blood circulation. It usually affects both legs at once and is associated with rough, scaly skin and itchiness.

Contact Dermatitis Allergic contact dermatitis occurs when the skin comes into contact with an allergen, such as certain metals or poison ivy. The skin can become red, swollen, and blistered, but this type of reaction doesn’t usually cause a fever. Oftentimes the rash of contact dermatitis will form the shape of the allergen — for example, a rash that circles the wrist suggests that a watchband may be to blame, or a rash in a straight line across the ankle mimics the path of the poison ivy leaf that brushed against the skin.

Eczema Atopic dermatitis, or eczema, tends to cause itching, red or scaly skin, and sometimes raised bumps that leak and crust over. It can occur anywhere on the body and does not favor the legs.

Shingles Caused by the virus that causes chickenpox, shingles causes a painful rash that usually appears as a row of blisters. It can occur anywhere on the body but is usually limited to one side at a time.

Tinea Pedis Also known as athlete’s foot, this common fungal infection typically causes redness, itchiness, scaly skin, and sometimes blisters and cracking of the skin on the feet.

Gout Gout occurs when uric acid crystals form in a joint, causing pain, swelling, and stiffness. Gout can also cause the skin over the affected joint to appear red and feel warm to the touch.

Deep Vein Thrombosis A blood clot, or thrombosis, in a deep vein of the leg can cause swelling, pain, and warmth. Like cellulitis, deep vein thrombosis usually happens in only one leg at a time. You should seek medical help if you have signs or symptoms of deep vein thrombosis.

Vein Inflammation Known as phlebitis, inflammation in a vein can cause pain, swelling, redness, and warmth. Phlebitis can be caused by deep vein thrombosis and also by varicose veins. You should seek medical attention if you develop symptoms of phlebitis.

Lipodermatosclerosis Lipodermatosclerosis refers to changes in the skin of the lower legs caused by inflammation of the layer of fat underneath the skin. The skin may become reddish and harder and darker in color than usual. The leg itself may become swollen, and the condition can be painful. One or both legs may be affected. You should seek medical help if you have signs or symptoms of lipodermatosclerosis.

Duration of Cellulitis

The good news about cellulitis is that it responds quickly to treatment. In most cases, your doctor will prescribe medication to take at home for 10 to 14 days, and you may start to feel better within a few days of starting the oral antibiotic — although you should be sure to take all of the pills prescribed. The length of treatment depends on the severity of the infection. (6)

But if you have severe cellulitis, you may need to receive antibiotics intravenously, requiring a hospital stay. The average hospital stay for cellulitis treatment is just over one week, according to the AAD. (8)

“When symptoms progress quickly or become severe, go to the emergency room,” advises Shainhouse.

Cellulitis Treatment Options

Treatment of cellulitis depends on the severity of the condition. In most instances, an oral antibiotic should take care of the infection. But some cases may require intravenous antibiotics administered in a hospital setting.

While taking an oral antibiotic, continue to monitor your symptoms. As a general rule of thumb, your symptoms should improve, not worsen. If they don’t show signs of improvement after three days of starting treatment, contact your doctor immediately. (6)

If you’ve had cellulitis more than three or four times in the past year, your doctor may prescribe a low-dose antibiotic to take long-term as a preventive measure, notes Johns Hopkins Medicine. (9)

How to Prevent Cellulitis

One of the best strategies for preventing cellulitis is to practice proper first aid when you have a skin injury.

For a minor cut or scratch, that generally means cleaning and covering the wound yourself or with the help of a companion.

But if you have a cut that is deep (¼ inch or deeper) or large, a puncture wound (a tack or nail in your foot, for example), an animal or human bite, a burn or scrape over a large area of your body, or a wound that continues bleeding after 10 to 15 minutes of applying direct pressure, you should seek medical attention from your doctor, in the emergency department, or an urgent care center. (5)

First aid for a minor skin injury is as follows:

  • Stop any bleeding by applying direct pressure to the wound, ideally with a clean cloth.
  • Wash the wound to remove dirt and debris. Use warm soapy water, if it’s available. If you’re not near modern plumbing facilities, use the cleanest water you can find to thoroughly rinse the wound. Scrub gently with a clean washcloth, if necessary. If you cannot get all of the dirt out of a wound, you should see a doctor to fully clean the wound.
  • Dry the wound and apply a thin layer of a topical antibiotic ointment, if desired.
  • Cover the wound with a bandage to keep it clean and lower the risk of dirt and bacteria entering the wound.
  • Change the bandage daily until the wound heals.
Special Precautions for People With Diabetes

People with diabetes, in particular, “should take meticulous care of their feet and be aggressive with treating even minor skin issues,” says Dr. Adalja. “Athlete’s foot (fungal infections on the feet) can cause skin to be more prone to bacterial infection, so this should be treated promptly. Also, they should receive routine podiatric care.”

11 Tips to Protect Your Feet and Legs if You Have Diabetes

If you have diabetes, examine your feet daily for redness, areas of warmth, signs of pressure or rubbing from shoes, blisters, or injuries of any type. Apply moisturizer to your feet to prevent cracking, but avoid putting moisturizer in the areas between your toes. In addition, keep your toenails and fingernails trimmed to prevent injury from scratching. (9)

Reducing Cellulitis Risk

Addressing the underlying risk factors for cellulitis can also help to prevent it. Such measures might include:

  • Losing weight if you’re overweight
  • Quitting smoking if you smoke
  • Restricting alcohol consumption to no more than one drink per day for women and no more than two drinks per day for men, per the AAD (10)
Spotting an Infected Wound

Even with the best first aid, infections can still occur. In this case, early detection is key to avoiding serious complications. Signs of an infected wound include:

  • Increasing redness and pain
  • Pus or oozing liquid at the site of the wound
  • Swelling
  • Tenderness
  • Itching

Cellulitis Complications and How to Prevent Them

Untreated cellulitis can lead to some serious medical conditions, including:

  • Infective endocarditis (infection of the endocardium, the layer of tissue that lines the chambers of the heart) (11)
  • Glomerulonephritis (kidney infection) (12)
  • Lymphadenitis (infection of the lymph nodes) (13)

Another major complication is the infection spreading to your bloodstream, at which point the infection becomes life-threatening. (9)

You can raise your chances of heading off complications by doing the following:

  • See a doctor if you have signs or symptoms of cellulitis.
  • Take your prescribed antibiotics as directed, and don’t stop the medication early.
  • Notify your doctor if your symptoms don’t improve within three days of starting an antibiotic.
  • Get plenty of rest to help your body heal faster. If the cellulitis is in your leg, elevate it to reduce swelling.

Research and Statistics on Cellulitis

Learn Some More Facts About Cellulitis

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