What Is Cellulitis?

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Thrombophlebitis in human leg

Cellulitis is a skin infection. It affects the layers under the skin’s surface and deep tissues underneath the skin. While cellulitis is relatively common and usually very treatable, it can become very serious. More than 14 million Americans develop cellulitis each year. Without proper treatment, cellulitis can spread through the blood and lymph system causing widespread infection.

What causes cellulitis?

Bacteria cause cellulitis. There are many different types of bacteria that can cause the infection. However, the most common culprits are Staphylococcus and Streptococcus bacteria. One strain—MRSA (methicillin-resistant Staphylococcus aureus)—has become a common cause of cellulitis in recent years. MRSA poses a serious health threat because it is resistant to several antibiotics that used to work against it.

In most cases, cellulitis is not a contagious infection. It typically does not spread from person to person. Instead, it occurs when bacteria normally living on the skin gain entry to the body. These bacteria usually aren’t harmful when they remain on the skin. In cellulitis, they enter through breaks in the skin. This could include scratches, cracks, cuts, sores, burns, insect bites, tattoos and piercings.

Covering wounds and other breaks in the skin with bandages helps keep bacteria out. But even uncovered wounds won’t necessarily lead to cellulitis in every case. Often, the body’s immune system takes care of the bacteria before they can cause a full-blown infection.

Certain things make cellulitis more likely to develop. Risk factors include:

  • Chronic medical conditions, such as diabetes

  • Obesity and being overweight

  • Older age

  • Poor circulation and lymphedema, which is chronic swelling in the arms and legs

  • Skin conditions, such as eczema

  • Weakened immune system, such as with cancer or HIV

It is also possible to develop cellulitis on skin areas that show no obvious signs of breakage. Having any of the risk factors above increases the chances of this happening. Having cellulitis once also increases the risk of getting it again.

What are the symptoms of cellulitis?

Cellulitis symptoms usually occur on one side of the body, such as one arm or leg. If both sides have symptoms, the cause is likely to be something else. Symptoms of cellulitis include:

  • Pain or tenderness

  • Redness that expands or grows. The edges of the red area are usually not sharp. Instead, the border transitions gradually to normal looking skin.

  • Red streaks, blisters, open sores, or pus-filled bumps

  • Swelling, firmness and warmth

  • Swollen lymph nodes in the area

You may also have general symptoms of infection. This includes fever, chills, cold sweats, and fatigue. Rapid heart rate, trouble concentrating, nausea, and drowsiness can also occur.

Cellulitis can affect any area of the body. In adults, cellulitis on the leg or foot is most common. Cellulitis on the face or neck more commonly occurs in children. A specific type of cellulitis affecting the face in young children is periorbital cellulitis, or preseptal cellulitis. In this case, the infection affects the eyelid tissues, usually on one side. The eyelid can swell to the point the eye closes. However, the eyeball itself and vision is normal.

Cellulitis can turn into a serious infection very quickly. Seek immediate medical care if you have symptoms of cellulitis or an area of redness that is growing or changing rapidly.

How is cellulitis treated?

Because cellulitis is a bacterial infection, it requires antibiotics to clear the infection. Your doctor will prescribe an oral antibiotic for 7 to 10 days. In severe cases, hospitalization with IV antibiotics (administered into the bloodstream through a vein) may be necessary for the most rapid treatment. If cellulitis turns into an abscess, surgery may be necessary to drain it and clear the infected tissue.

Symptoms should begin to improve within a few days of starting the antibiotic. However, it is important to finish the whole course, even after you start to feel better. Failing to take the entire course of antibiotics can allow the infection to return. And it may be more difficult to treat a second time.

Wound care can also be part of cellulitis treatment. You may need special wound coverings or dressings. Caring for your wound as directed will help your skin heal. For cellulitis on the leg or arm, elevating it will help reduce swelling.

Fighting the infection is stressful for your body. While your body is healing, rest is important.

Can cellulitis be prevented?

Once you have cellulitis, it is easy to get it again. You can’t always avoid skin injuries. So, when you have a wound or break in the skin, take care of it right away. Wash the wound and apply antibiotic ointment. Then use a bandage large enough to cover the whole wound. Wash the wound and change the bandage daily or whenever it gets dirty.

Other skin care tips for people at risk of cellulitis or who have already had it:

  • Check your feet daily.

  • Maintain a healthy body weight.

  • Moisturize your skin regularly to prevent dryness, cracks and peeling.

  • Protect your hands with gloves and wear proper footwear.

  • Stop smoking and limit alcohol use.

  • Treat other medical conditions to effectively control them, with medication if necessary.

  • Trim your nails regularly taking care not to injure surrounding skin.

  • Use sites other than an arm that has had cellulitis for blood draws.

If you get recurrent bouts of cellulitis, your doctor may recommend a prolonged course of a low-dose antibiotic to prevent future episodes.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2019 Jun 28
  1. Cellulitis. American Academy of Dermatology. https://www.aad.org/public/diseases/rashes/cellulitis#overview 
  2. Cellulitis. American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/what-is-cellulitis 
  3. Cellulitis. Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/cellulitis/symptoms-causes/syc-20370762 
  4. Cellulitis. Merck Manual Consumer Version. https://www.merckmanuals.com/home/skin-disorders/bacterial-skin-infections/cellulitis?query=Cellulitis 
  5. Cellulitis. Nemours Foundation. https://kidshealth.org/en/parents/cellulitis.html 
  6. Preseptal Cellulitis. Merck Manual Consumer Version. https://www.merckmanuals.com/home/eye-disorders/eye-socket-disorders/preseptal-cellulitis 


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