What are the other Names for this Condition? (Also known as/Synonyms)

• Skin Cellulitis

What is Cellulitis? (Definition/Background Information)

• Cellulitis is a common but potentially serious skin condition caused by a bacterial infection. It affects the inner skin layers (dermis), including the subcutaneous tissues, resulting in the formation of red patches or plaques, often on the lower limbs and face, although they occur anywhere on the skin
• Without adequate treatment, Cellulitis may lead to severe complications including widespread systemic infections that can be life-threatening. The condition is more frequently observed in older adults and immunocompromised individuals
• A diagnosis of Cellulitis may require physical exams, blood tests, and skin swab or fluid culture to detect the causative bacteria. Sometimes, a small tissue sample is taken for culture. Antibiotics are the mainstay of treatment for Cellulitis. Also, maintaining personal hygiene and cleanliness is important in early resolution of the condition

Who gets Cellulitis? (Age and Sex Distribution)

• Cellulitis may affect individuals of any age; although, middle-aged and elderly adults are more prone to developing the condition
• It affects both males and females without any predilection
• There is no preference for any racial or ethnic group, and the condition is seen worldwide

What are the Risk Factors for Cellulitis? (Predisposing Factors)

The risk factors associated with Cellulitis may include:

• Older adults and individuals with weak immune systems are more susceptible to the condition
• Pre-existing wounds, skin ulcers, or surgical wounds
• Insect bites, leech bites, and animal bites
• Poorly-controlled diabetes
• Individuals who are overweight or obese have a higher risk
• HIV infection or AIDS
• Use of medication that can suppress the immune system
• Any other condition that causes a weak or poor immunity (such as organ transplant, chronic illness, recent surgeries, etc.)
• Individuals, who had Cellulitis earlier, have an increased risk for recurrence of the condition
• Skin disorders such as psoriasis and eczema
• Fungal infections such as athlete’s foot
• Chronic alcoholism
• Cancer treatment such as radiotherapy and chemotherapy
• Pedal edema (swollen feet)
• Varicose veins
• Individuals with chronic liver or kidney disease
• Conditions causing ulceration of leg such as stasis dermatitis
• Cracked heels
• Use of recreational drugs via injections
• Pregnancy
• Densely populated residential facilities such as home shelters, dormitories, army barracks, etc.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Cellulitis? (Etiology)

Infection by the following bacterium can cause Cellulitis:

• Commonly, it is caused by Streptococcus pyogenes (Group A Streptococcus) and Staphylococcus aureus
• Occasionally, Aeromonas hydrophila, Haemophilus influenzae, Erysipelothrix, Pasteurella multocida, Pseudomonas aeruginosa, Streptococcus viridans, and Vibrio vulnificus are causative

Typically, these bacteria enter human skin through open cuts and wounds, or weaknesses in the skin. Cellulitis resembles another skin infection, termed impetigo, which involves the superficial skin layers (epidermis). Erysipelas is another superficial skin infection, by definition more superficial than Cellulitis, but this term is often used interchangeably with Cellulitis.

What are the Signs and Symptoms of Cellulitis?

The signs and symptoms of Cellulitis may vary from one individual to another and may be mild or severe. The infection typically affects the lower legs (usually in adults) or the face (usually in children).

The signs and symptoms of Cellulitis may include:

• Fever, chills, and shivering may form the initial presentations
• Localized redness and swelling may be seen on one leg, or on one side of the face
• The affected skin may present “fine dimples”, or an orange peel appearance from accentuation of the follicular openings
• The infection may penetrate deeper into the skin layers in severe cases, and present bleeding (purpura)
• The skin may blister and present ulceration, followed by necrosis (tissue death)
• Abscess formation
• Pain and discomfort may be noted
• Swollen lymph nodes
• In some cases, bulla (large blisters filled with fluid) may be observed

Additional signs and symptoms of the underlying condition, if any present, may be noted.

How is Cellulitis Diagnosed?

The diagnosis of Cellulitis may involve the following tests and procedures:

• Complete evaluation of medical history along with a thorough physical exam, including examination of the skin sores and blisters
• Dermoscopy: It is a diagnostic tool where a dermatologist examines the skin using a special magnified lens
• Wood’s lamp examination: In this procedure, the healthcare provider examines the skin using ultraviolet light. It is performed to examine the change in skin pigmentation
• Complete blood count (CBC), C-reactive protein test, and antibody tests
• Blood or wound culture: A culture may be performed to confirm the presence of bacteria and to rule-out other causes of infection. In this culture, a small amount of pus or fluid from one of the sores is collected and sent to the lab for testing. The test results can help confirm the presence and type of bacteria (if any)
• Imaging studies, such as CT or MRI scans, may be necessary in some cases
• Skin biopsy: A skin biopsy is performed and sent to a laboratory for a pathological examination. In suspected Cellulitis cases, particularly if an uncommon pathogenic bacterium is suspected, tissue is sometimes sent in culture medium instead of formalin to grow bacteria. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed), and with microscope findings, the pathologist arrives at a definitive diagnosis

Tests and procedures to diagnose the associated condition, if any present, is important.

A differential diagnosis to eliminate other conditions may be considered, before arriving at a definitive diagnosis. These may include:

• Conditions causing pseudocellulitis
• Deep venous thrombosis
• Drug eruption
• Severe allergic contact or toxic dermatitis
• Gas gangrene
• Lyme disease
• Necrotizing fasciitis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Cellulitis?

The complications of Cellulitis are uncommon, but may include:

• Emotional stress due to cosmetic concerns
• Gangrene formation in the lesions if severe skin ulcers are left untreated. This can be an emergency medical situation
• Formation of blood clots (in the leg) resulting in thrombophlebitis
• Systemic infection when the whole body is involved/affected 
  • Infection of the bone and joints causing bursitis, septic arthritis, or tendonitis
  • Involvement of the heart valves due to infective endocarditis
  • Involvement of the kidneys causing glomerulonephritis in children
  • Involvement of the brain leading to cavernous sinus thrombosis
  • Sepsis
• Recurrence of the condition due to lymphatic drainage and/or presence of predisposing factors; some individuals are known to have multiple recurrences
• Treatment complications from antibiotic resistance

Complications of the underlying condition, if any present, may be noted.

How is Cellulitis Treated?

The treatment measures for Cellulitis may include:

• Employing hygienic measures, such as keeping the skin region clean
• Symptomatic treatment may involve the administration of painkillers, increased fluid intake, use of ice packs for local discomfort, and use of compression stockings
• If the legs are involved, keeping it elevated, such as by propping it up on a pillow, to decrease swelling
• The areas around the blisters should be gently washed with soap and running water
• The affected area should be covered lightly with gauze to prevent the spread of infection
• Oral antibiotics, such as penicillin, may be prescribed for mild infections and intravenous (broad-spectrum) antibiotics for severe infections
• Hospitalization is necessary for severe systemic infections
• Abscess drainage, removal of dead tissue, and treatment of compression symptoms may be undertaken through minor surgical procedures 

Undertaking treatment of the underlying/associated condition may be necessary.

How can Cellulitis be Prevented?

Following are some of the precautionary measures for preventing Cellulitis:

• Always keep the skin clean and healthy; in case of dry skin, the use of suitable moisturizers is recommended
• Cuts, scrapes, insect and animal bites, and wounds must be washed immediately, and antibiotic ointment applied, to prevent further spread of the infection
• Wearing gloves while applying ointment on the blisters is advised. Washing the hands after applying ointment on the blisters is recommended
• Items used by the infected individual, such as towels, clothing, bedding, etc., should be washed or cleaned everyday
• Avoid sharing clothes, towels, bed, and any other item of the infected individuals
• The nails of infected children should be cut short so that further infection from scratching the blisters can be avoided
• Application of soothing solutions (calamine or oatmeal-based) on the lesions may reduce itchiness
• Frequent washing of hands is recommended
• The infected child or adult is best advised to stay inactive, until he/she recovers fully
• In case of a higher risk for recurrence of Cellulitis, the healthcare provider may recommend the use of prophylactic antibiotics
• Getting treatment for any underlying medical condition(s) that may decrease immunity in the individual

The entire course of medication prescribed by the healthcare provider should be completed for effective cure and prevention of recurrence.

What is the Prognosis of Cellulitis? (Outcomes/Resolutions)

The prognosis of Cellulitis is good with appropriate and prompt treatment. However, the prognosis also depends upon the severity of the infection, development of complications, overall health status of the individual, promptness of treatment, and the individual’s response to treatment.

• With appropriate treatment, the skin condition may subside within about 7-10 days; although for the skin to return to normalcy, it may take some additional time
• Individuals with an underlying immune deficiency disorder and the elderly may be affected more than the others
• Recurrent episodes of Cellulitis are noted if the causative factors are not addressed
• Development of severe complications from systemic infection is known to result in fatalities

Additional and Relevant Useful Information for Cellulitis:

Cleaning the skin too hard with strong chemicals or soaps may aggravate the skin condition. Care must be taken avoid strong soaps and chemicals that could potentially worsen the condition.