Cellulitis: Symptoms, Diagnosis, Causes & Treatment

Updated in July 2023

Cellulitis occurs when bacteria penetrates the skin and infects its deepest layers. It causes symptoms like skin redness, pain and swelling, and is most commonly seen in the lower extremities. 

Contrary to cellulite, cellulitis can lead to serious complications like septicemia, which is a systemic infection in the whole body, or even death if left untreated. 

If you suspect you may have a skin infection, you should proceed to the emergency room for diagnosis and treatment, which usually involves the use of antibiotics. 

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Main symptoms

Some symptoms that can appear with cellulitis are: 

  • Pain in the affected area
  • Extensive red areas throughout the body 
  • Fever over 38ºC (100.4ºF) 
  • Skin that is swollen and may exude pus 
  • Swollen lymph nodes near the affected area 

In more serious cases, symptoms may also include tremors, chills, fatigue, dizziness, excessive sweating and muscular pain. Symptoms like drowsiness, blisters or welts on the skin may be a sign that the infectious is worsening. 

All of these symptoms may be a sign of another type of skin infection, like erysipelas, which is an illness affects the most superficial layers of the skin. Therefore, you should see a doctor if you have symptoms, so that the right diagnosis and treatment can be started. 

Confirming a diagnosis 

In most cases, cellulitis is diagnosed by a dermatologist through assessment of the patients’s signs and symptoms. However, because the symptoms can present very similarly to other diseases (like erysipelas), the doctor may order bloodwork or lab specimen testing of the skin to confirm the type of bacteria causing the infections. 

Cellulitis vs erysipelas 

The main difference between cellulitis and erysipelas is that depth of skin affected: erysipelas is usually found in the superficial layers of the skin, while cellulitis is found in the deepest layers. Other factors that help to differentiate these two conditions include: 

Erysipelas Cellulitis
Superficial infection Infection in the deepest layers of the derma and subcutaneous tissue 
It is easy to identify the skin that is infected and not infected by observing the rashes  It is difficulty to identify the skin that is infected and not infected, as it causes small rashes 
Most commonly seen in the lower extremities and face Most commonly seen in the lower extremities

The signs and symptoms of these diseases are very similar, which is why a family doctor or dermatologist should examine the affected areas and order testing. They will be able to identify the underlying cause and orient treatment as necessary. 

Possible causes 

Cellulitis occurs when bacteria like Staphylococcus or Streptococcus penetrate the skin. It is more commonly diagnosed in people with recent surgical incisions or with wounds that were left untreated.

People with skin problems that cause irregular skin growth, like eczema, dermatitis or a fungal infection, are also at a higher risk for developing cellulitis. Those with a weakened immune system are also at greater risk. 

Is cellulitis contagious?

In healthy people, cellulitis is not contagious, as it does not easily transfer from one person to another. However, if you have a wound or skin-related illness, bacteria is at a greater risk enter in contact with the compromised skin and develop into a cellulitis. 

Treatment options

Treatment for cellulitis is usually done with antibiotics, like clindomycin or cephelexin, given over 10 to 21 days. Antibiotics should be taken at the same times and the skin should continue to be monitored. Any worsening should be reported to the doctor, as the antibiotic may not be working as expected and require switching. 

The doctor may also prescribe analgesics, like acetaminophen, to relieve symptoms during treatment. It is also important to regularly examine the skin, to follow-up with adequate wound care and dressing changes as needed, and to apply topical moisturizers or antibiotics as indicated in your treatment plan. 

Symptoms typically start to improve within 10 days of antibiotic use. However, if symptoms worsen, the doctor may consider an alternative antibiotic or even consider admission to the hospital, where IV antibiotics can prevent spreading of the cellulitis to the rest of the body.