What Is the Main Cause of Cellulitis?

What is cellulitis?

Cellulitis is a common skin infection. Bacterial infection is the main cause of cellulitis.
Cellulitis is a common skin infection. Bacterial infection is the main cause of cellulitis.

Cellulitis is a common skin infection. It can happen to anyone, and if left untreated, it can lead to potentially life-threatening illnesses. Knowing the symptoms of cellulitis will help you recognize it quickly, get the right treatment, and avoid long-lasting and dangerous complications.

Cellulitis is a noncontagious bacterial infection of the deeper layers of your skin. It usually looks like a red rash, which can be warm to the touch, swollen, and sore or painful. It’s important to see your doctor as soon as possible if you get cellulitis.

Signs and symptoms of cellulitis

Cellulitis is a skin infection, but symptoms may appear in other parts of your body. 

Rash on the skin 

With cellulitis, you'll develop a red rash that appears most often on the legs but can happen anywhere on the skin. The rash may blend into your skin at its edges, so it’s hard to tell where it stops. The rash and the area around it may also be warm to the touch, swollen, tender, or sore. The skin could also look pock-marked, glossy, and have blisters filled with yellow fluid.

Swollen glands

You may notice swollen lumps on the sides of your neck, under your chin, your underarms, or inner thighs. This is a sign that your body is fighting an infection.


Cellulitis can cause a fever of 100ºF or more in some people.

Types of cellulitis

Cellulitis can have different names and characteristics depending on where it develops on your body. 

Buccal cellulitis 

Buccal cellulitis develops on your cheek. This most often happens to very young children under a year old. It sometimes occurs alongside a tooth problem.

Perianal streptococcal cellulitis 

Perianal streptococcal cellulitis develops in and around your anal and rectal areas. This type occurs most often in children.

Preseptal cellulitis 

Preseptal cellulitis develops in your eyelid and at the front of the eye, and is most common in children under five years old. It can cause swelling, redness, warmth, and pain in the upper and lower eyelids and other areas near the eye.

Orbital cellulitis 

Orbital cellulitis grows behind the eye, and the eye sometimes looks normal even when you’re infected. The eyeball may turn red or bulge out, you may have trouble moving it or seeing out of it, and your upper and lower eyelids may swell, change color, or change texture. This is less common and often more dangerous than preseptal cellulitis. 

Causes of cellulitis 

In general, cellulitis is caused by bacterial infection. Certain types of bacteria — often referred to as strep and staph — normally live inside your mouth and nose, and on the surface of your skin. Your skin is several layers deep. Cellulitis infections happen when the bacteria are able to get past the surface of your skin and reach the deeper layers, which can happen in a variety of ways.

Open wounds

Breaks in the skin due to injury or infection are a common pathway for bacteria. Cuts, open sores, insect bites, eczema, and even fungal infections like athlete’s foot can lead to cellulitis.

Sinus infections 

Sinus infections are one of the most common causes of orbital cellulitis behind the eye. Your sinuses are empty pockets within your skull that can get infected with certain bacteria. However, this is rare, since there is a vaccine that helps protect against some of these bacteria.

Immune system suppression

The immune system is meant to keep harmful bacteria on the surface of our skin at bay. People with suppressed immune systems due to certain medications, HIV/AIDS, diabetes, or other conditions may be at higher risk of getting cellulitis.

When to see the doctor for cellulitis

It’s important to see the doctor as soon as possible if you think you have cellulitis. Left untreated, it could lead to sepsis, a potentially fatal illness. It can also lead to serious infections that can damage your bones, blood, skin, and joints.

Diagnosis for cellulitis

A doctor can diagnose cellulitis by examining your skin and rash. They may order lab tests such as a blood or skin sample to show what type of bacteria is causing the issue. This information helps them prescribe the right antibiotic.

Treatments for cellulitis

In most cases, a doctor will prescribe you an antibiotic pill to kill the bacteria. Always follow their directions exactly, even if the condition seems to worsen a few days after starting your medication. Ask your doctor about any concerning symptoms that occur after you begin treatment. If the infection is on your leg, the doctor may also recommend that you keep the leg elevated.

Cellulitis may require a hospital visit if you’re experiencing persistent nausea and fever, eye infection symptoms, or worsening of the skin rash long after you begin antibiotics.


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American Academy of Ophthalmology: "What is Cellulitis?"

American Academy of Pediatrics: "Pinpointing origin of facial cellulitis key for treatment."

American Family Physician: "Perianal Streptococcal Dermatitis."

Cedars-Sinai: "Cellulitis."

Centers for Disease Control and Prevention: "Cellulitis: All You Need to Know."

Children’s Hospital of St. Louis: "Cellulitis of the Eye."

Harvard Health Publishing: "By the way, doctor: Can you tell me more about cellulitis?"

Harvard Health Publishing: "Cellulitis."

Johns Hopkins Medicine: "Cellulitis."

Mount Sinai: "Orbital cellulitis."

National Health Service: "Cellulitis."

National Health Service: “Swollen glands."

NHS Inform: "Cellulitis."

Penn Medicine: "Cellulitis."

Sepsis Alliance: "Cellulitis."