Necrotizing Fasciitis vs. Cellulitis: the signs and symptoms of skin and soft tissue infection

May 27, 2022

Burn and Reconstructive Centers of America (BRCA) serves communities across the country with burn, wound and reconstructive care and managing skin and soft tissue disorders and infections. In the event of burns, wounds, cuts or surgical incisions, the body becomes susceptible to bacterial colonization and infection. These infections can range from minor to life-threatening depending on the patient’s health, the kind of infection and how long the infection has been untreated.

BRCA’s headquarters, the Joseph M. Still (JMS) Burn Center of Augusta, GA, is the largest burn center in the country. Our healthcare teams treat a continuum of common and rare skin and soft tissue infections. Examples of these infections are cellulitis, staphylococcal scalded skin syndrome, toxic shock syndrome (TSS), deep soft-tissue infections, Fournier’s gangrene and necrotizing fasciitis. The most common infection of those listed is cellulitis. Conversely, necrotizing fasciitis is one of the rarest skin and soft tissue infections that is commonly treated at our burn centers. Besides their contrasting prevalence in our patient population, what else makes these two skin and soft tissue infections different from each other and detrimental to those susceptible to them?


What is cellulitis?

Cellulitis is a common, non-invasive bacterial skin and soft tissue infection that typically develops from animal bites, surgical sites, sores, burns, diabetic wounds and many other types of open wounds or broken skin injuries. However, according to the Centers for Disease Control and Prevention (CDC), cellulitis can occasionally develop without an open wound pathway into the body, leaving experts perplexed about how the cellulitis infection process works. Different bacteria can cause the onset of cellulitis, the most common bacterial culprits are streptococcus and staphylococcus.

Who is at an increased risk of developing cellulitis?

While this type of infection cannot be passed from person to person, people can get cellulitis multiple times throughout their lives, especially if they are at an increased risk. Those at an increased risk of developing cellulitis are:

  • Geriatric patients or the elderly due to their weakened immune systems and proximity to assisted living homes, nursing homes, retirement communities, etc.
  • Diabetics
  • Those using injectable drugs
  • Those suffering from chronic skin conditions such as eczema or athlete’s foot
  • Those who have or have had chickenpox or the shingles virus
  • Those with lymphatic system conditions such as lymphedema
  • Bariatric patients or those who are considered overweight
  • Those suffering from other comorbidities or a weakened immune system

What are the signs and symptoms of cellulitis?

Cellulitis is a bacterial infection of the lower layers of skin and tissue, also considered a subdermal infection/subcutaneous infection, that is contained within the skin. Therefore, it isn’t typically a surface-level infection but a deep infection that can appear anywhere on the body, most commonly in the lower extremity. While cellulitis can begin as a localized infection of a wound bed or a specific part of the body, if left untreated, it can spread to other areas of the skin or tissue, the bloodstream or the lymph nodes causing more severe infections such as necrotizing fasciitis or a generalized, whole-body infection (sepsis).

Signs and symptoms of cellulitis include:

  • Edema (swelling)
  • Hyperesthesia (increased sensitivity of the skin)
  • Erythema (skin rash or irritation)
  • Induration (hardening or toughness of the affected area)

Along with those, you may experience:

  • Skin that is warm to the touch
  • Skin that appears pitted, like the outside of an orange (the clinical term is peau d’orange)
  • A wound bed that is changing colors (if there is a wound)
  • A wound bed that develops a foul odor (if there is a wound)
  • Blistering of the skin
  • Fever
  • Chills

How is cellulitis diagnosed?

Healthcare professionals will conduct a physical examination and use the signs and symptoms listed above to help diagnose this infection. Typically, no lab tests or blood work are involved in diagnosing cellulitis. Occasionally a biopsy is done.

What treatment options are available?

As with most infections, cellulitis is best treated through antibiotics. Those suffering from cellulitis may be treated with a systemic antibiotic for milder infections or antimicrobial delivered intravenously (IV) for more severe cases. A systemic antibiotic treats the whole body, not just the affected area, in hopes of destroying the causative agent and preventing the infection from spreading. For those with open cuts or wounds that have been infected, the systemic antibiotic may be supplemented with topical antibiotics, the surgical excision of the infected area and the placement of skin grafts. If the affected area involves an appendage (arm, leg, foot or hand), keeping the appendage elevated above the heart may help to reduce swelling and progress the healing process.

What is the outlook for those with cellulitis?

While comparatively cellulitis is considered a minor infection, it can progress into a medical emergency or cause life-threatening complications if left untreated. If left untreated, cellulitis can continue to spread, eventually turning into sepsis (a full-body infection) or worsen and develop a secondary infection such as necrotizing fasciitis (a flesh-eating bacterial infection). If treatment is rendered and the cellulitis infection continues to grow or spread, this might be a sign of antibiotic-resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), which is becoming increasingly common. Some other rare but possible medical complications include:

  • Blood infection or sepsis
  • Joint infection or septic arthritis
  • Bone infection (osteomyelitis)
  • Inflammation of the lining of the heart or heart valves (endocarditis)
  • Inflammation of the veins causing blood clots or decreased circulation
  • Limb loss

Once cellulitis develops into sepsis or necrotizing fasciitis, the infection becomes life-threatening and requires aggressive medical intervention to stop the disease from spreading and heal the body. Don’t wait to seek medical attention. If you do have cellulitis, it is best to have it diagnosed and treated as soon as possible to avoid more severe complications. If you notice rapid spreading of redness or swelling in the affected area or you’ve developed a fever, the infection is rapidly progressing and requires medical intervention immediately.

Necrotizing Fasciitis

What is necrotizing fasciitis?

Necrotizing fasciitis, also known as flesh-eating disease, is a rare bacterial infection that causes the necrosis or death of subcutaneous tissue and fascia (the tissue under the skin, nerves, fat and blood vessels) but can progress to include the skin and muscle. According to the CDC, this infection can develop from blunt force trauma without an open wound pathway into the body. However, necrotizing fasciitis typically develops from cellulitis or the same bacteria as cellulitis, streptococcus, staphylococcus and a host of other bacteria such as vibrio and clostridia, though it can also enter the body as a primary infection via an open wound (cut, scrape, puncture, surgical site, etc.), burn or insect bite.

Due to the varying bacteria that can cause the development of necrotizing fasciitis, this infection is classified into four categories based on the type of bacteria behind the flesh-eating disease.

Type I Infection

The most common type of fasciitis diagnosed is a type I infection. It accounts for roughly 70% to 80% of cases and consists of various kinds of bacteria. Most of these infections begin within the groin and abdominal areas.

Various species make up this type of infection, including streptococcus and anaerobes. Older people are most likely to acquire skin-eating bacteria of this type. They often have other comorbidities, including obesity or immunodeficiencies.

Type II Infection

Type II infections make up 20% to 30% of cases and chiefly involve a patient’s extremities. Streptococcus pyogenes bacteria are the main driving force of this flesh-eating bacteria. It may appear along with or together with staphylococcal infections. Both types of skin-eating bacteria can spread rapidly and lead to toxic shock syndrome (TSS).

Unlike type I infections, type II infections are more common in younger people. It is also exclusively developed through a traumatic injury of some kind.

Type III Infection

Type III infections are caused by bacteria commonly found in saltwater (such as vibrio). It is rare and displays a similar necrotizing progression as type II necrotizing fasciitis. However, it lacks the same visible skin symptoms, resulting in its presence not being immediately apparent, particularly in the case of early-stage flesh-eating bacteria.

Type IV Infection

Few cases of type IV infection have been found among humans but are caused by fungal infections. Due to how rare it is, little in-depth research has been conducted into diagnosing and treating a type IV infection. However, this type of infection is found typically in immunocompromised individuals and can happen as a result of trauma.

Who is at an increased risk of developing necrotizing fasciitis?

While most cases of necrotizing fasciitis occur randomly, this infection can be transmitted. Though rare, a person who develops necrotizing fasciitis can potentially pass the infection to someone who is immune-compromised or at an increased risk of infection. Those at an increased risk of developing necrotizing fasciitis are:

  • Diabetics
  • Young children suffering from chickenpox
  • Adults 50 years of age and older
  • Bariatric patients or those who are considered overweight
  • Those who have cellulitis or a history of cellulitis
  • Those who have cancer or a history of cancer
  • Those who are immune-compromised
  • Those suffering from renal (kidney) disease or failure
  • Those suffering from scarring of the liver (liver cirrhosis) or liver failure
  • Those suffering from hypertension or high blood pressure
  • Those using injectable drugs 

What are the signs and symptoms of necrotizing fasciitis?

This subdermal infection develops beneath the epidermis (first layer of skin), affecting the underlying dermis and subcutaneous tissues. With a morbidity rate as high as 50%, this infection is known to progress rapidly and be extremely life-threatening. Due to the rapidity of the infection process, signs and symptoms are broken up into two stages: early and late-stage infection.

The signs and symptoms of early-stage necrotizing fasciitis include:

  • Localized pain or pain specific to one area of the body that is out of proportion
  • Edema or swelling without discoloration
  • Fever
  • Pain, swelling or redness that is rapidly spreading

The signs and symptoms of late-stage necrotizing fasciitis include:

  • Induration (hardening or toughness of the affected area)
  • Paresthesia (skin tingling, prickling, numbness or burning) without apparent cause
  • Discoloration of the skin, including a dark, black or slightly bruised appearance
  • Blistering of the skin
  • Fever
  • Wound discharge that is abnormal in color or has a foul odor
  • Toxemia

Along with those, you may also experience:

  • Fatigue or exhaustion
  • Dizziness
  • Diarrhea, nausea or vomiting

How is necrotizing fasciitis diagnosed?

Early diagnosis is essential in limiting the damaging effects of this infection, but when it comes to diagnosing necrotizing fasciitis, it can be difficult, mainly if it develops as a secondary infection. The finding on the skin can be subtle since the disease directly affects the fascia underneath the skin. The signs and symptoms can be deceiving on their own and must be supplemented with imaging, lab tests and surgery for a definite diagnosis of necrotizing fasciitis. A definitive diagnosis step may include an X-ray of the subcutaneous tissues for evidence of gas buildup, a computed tomography (CT) scan, a magnetic resonance imaging (MRI) scan and biopsies of the affected area. While these tests may provide information on the bacteria present and the depth of the infection, to distinguish necrotizing fasciitis from other severe soft tissue and flesh-eating infections like myonecrosis, surgery is the only accurate way to differentiate the infection and establish a treatment plan.

What treatment options are available?

Due to the rapidity at which necrotizing fasciitis spreads and the high mortality rate, treatment should be rendered as early in the infection process as possible. The treatment plans for necrotizing fasciitis are more aggressive than cellulitis and much more invasive. Treatment of necrotizing fasciitis includes:

  • Intravenous (IV) antibiotics: aggressive broad-spectrum antibiotic treatment is delivered straight into the patient’s vein for systemic relief of the infection. However, the further along the infection is, the less likely the antibiotic will be able to reach all areas of the body as the veins are attacked and circulation is decreased or cut off.
  • Fluid resuscitation: fluid resuscitation involves replacing or replenishing the body’s fluids using the preferred Lactated Ringers (LR) solution or Normal Saline if LR is unavailable. Fluid resuscitation aims to maintain blood circulation (perfusion) and organ function while avoiding inadequate or excessive fluid replacement.
  • Debridement: this is a surgery to clean the affected area using pressurized water, chemicals or scrubbing devices to remove as much of the dead tissue and debris as possible, and is sometimes necessary upon arrival at the hospital. The first debridement surgery should be considered in-depth. With each additional debridement procedure, the mortality rate increases. It is typical to require multiple procedures to determine which areas are salvageable and those that need to be removed.
  • Excision of necrotic tissue: during this surgery, all of the dead tissue is cut out and removed.
  • Wound management: while the infection is still present, wounds cannot be closed. Therefore, proper wound management is essential. Wounds must be packed with anti-septic soaked dressings in conjunction with topical antimicrobial ointment.
  • Hyperbaric oxygen therapy (HBO): provides 100% oxygen at pressures greater than average atmospheric (sea level) pressure. This allows more oxygen to pass throughout a patient’s body to promote healing, fight infection and kill bacteria. It is unclear whether HBO helps alleviate necrotizing fasciitis. HBO therapy in conjunction with antibiotic treatment is sometimes utilized and can benefit the infection process of necrotizing fasciitis.
  • Radical surgical intervention: there comes the point at which the patient’s overall health must be considered, and radical surgical intervention must take place to save the patient. This typically involves amputation of the unsalvageable parts of the body, which commonly include the toes, fingers, feet, hands, all or part of the arm/s and all or part of the leg/s.

What is the outlook for those with necrotizing fasciitis?

Necrotizing fasciitis is considered a medical emergency for the acute detrimental effects and the severe and common complications that contribute to this infection’s fatality. Even with treatment, necrotizing fasciitis can lead to the development of sepsis (generalized whole body infection), septic shock, organ failure and toxic shock syndrome. Other necrotizing fasciitis complications include severe scarring and amputation from removing dead or infected tissue. Outlook usually involves reconstructive surgery to help recovery.

How can you prevent the development of necrotizing fasciitis and cellulitis?

Good hygiene and wound care are essential to maintaining overall health and preventing viral, fungal and bacterial infections. To help prevent the development of cellulitis, consider the following precautions:

  • Wash your hands frequently, especially when cleaning or bandaging open injuries (broken blisters, scrapes, cuts, punctures, ulcers, wounds, burns, etc.)
  • Clean all open injuries with gentle soap and tepid or slightly warm water
  • Apply an antibiotic ointment and cover all open injuries with a dry, sterile dressing or bandage
  • Avoid submerging the affected area in unsanitary water, such as lakes, oceans, hot tubs, swimming pools, etc.
  • Refrain from smoking. Smoking can slow the healing process and lead to chronic or non-healing wounds
  • Keep an eye on surgical sites and open wounds for changing color, smell or drainage
  • Those suffering from pre-existing conditions such as diabetes, lymphatic conditions, skin conditions and more should do what they can to manage their conditions, such as limiting sugar intake or speaking to their healthcare provider about what they can do to reduce their risk of cellulitis

So, what is the difference between necrotizing fasciitis and cellulitis?

The key differences between these two infections are:

  • Cellulitis is much more common, the mortality rate is much lower and the complications less frequent and less severe than those associated with necrotizing fasciitis.
  • Cellulitis is contained within the skin and necrotizing fasciitis is a much more severe infection under the skin.
  • Necrotizing fasciitis has a much more rapid infection process than cellulitis.
  • Necrotizing fasciitis’ infection process works by killing the tissue or causing tissue necrosis, while cellulitis can lead to tissue necrosis if left untreated and allowed to develop into a flesh-eating infection.
  • Necrotizing fasciitis can develop from unmanaged cellulitis.
  • Cellulitis is more easily diagnosed through a physical examination, while necrotizing fasciitis is more insidious.
  • The prognosis of patients with cellulitis is usually good and most often involves antibiotic treatment and debridement or excision procedures are less common, while necrotizing fasciitis can go on for much longer depending on the severity and how well the patient is responding to treatment.

In the end, comparing necrotizing fasciitis and cellulitis is like comparing a firecracker to a hand grenade. While both are bacterial infections, everything from the infectious disease processes to the diagnosing procedures is different, so neither should be self-diagnosed or cared for at home without consulting a healthcare professional.

Further Information

If you feel your burn, wound or traumatic injury is infected, the best action is to contact your provider or call our 24/7 burn information service at (855) 863-9595. It is best to treat the infection as early as possible to prevent further complications. Leaving an infection untreated may lead to graft loss, tissue death, amputation, full-body infection, etc.

For more information on different types of skin and soft tissue infection, please click here.

For more about how to treat an infected burn, please click here.

For more information about sepsis, please click here.

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