Cellulitis is an infection of the skin characterized by redness, swelling and pain. In most cases there is an associated fever and increase in white blood cell count, a marker of infection. It may be accompanied by spread in the lymphatic vessels seen as a red streak on the skin and/or swelling of the lymph glands. Infection causing organisms, like bacteria, enter the skin at sites of trauma or scratches, or through an already existing skin ailment, such as psoriasis, eczema or a fungus infection (athlete’s foot).

Erysipelas is also a type of skin infection; however, it involves only the superficial or surface layer of the skin. Cellulitis on the other hand extends down to deeper skin and into the fat. The cause of cellulitis is usually bacteria that have gained access through the skin from a break in the skin’s natural barrier. In adults the most common bacteria are group A streptococcus (“strep”) and Staphylococcus aureus (“staph”). In children younger than 3 years of age Haemophilus influenza type B may be implicated. However, with the use of routine vaccination this form of cellulitis has become much less common.

Cellulitis may develop on what appears to be normal skin or next to surgery sites or ulcers. There is no distinctive border between the infected and uninfected skin. The redness associated with the infection fades and blends into surrounding skin. Sometimes cellulitis can recur many times at a specific location on the body. Often when this occurs an underlying venous or lymphatic problem may exist, compromising the body’s circulation. Cellulitis that recurs on the leg can often be associated with a preexisting skin lesion like an ulcer or erosion. These areas act as portals or doors for the infection to enter through. The lymphatic drainage can be damaged by previous cellulitis, surgery with resection of the lymph nodes, and radiation therapy.

Diagnosis is made by the distinctive clinical appearance of cellulitis, which includes redness, warmth, swelling and pain. Often it is difficult to isolate or grow the causative bacteria, therefore cultures may or may not be helpful. Fever may be present. Several lab abnormalities (increase in the white blood cell count and an increase in the sedimentation rate) may indicate active infection in the body. These lab changes are indicative of inflammation and infection and are not entirely specific for cellulitis.

In patients with other medical conditions (diabetes, blood malignancies, intravenous drug abuse, HIV, or use of chemotherapy) the cultures are more likely to show presence of a bacterial organism. That organism tends to be different than the more commonly implicated “strep” or “staph” bacteria. Some of the bacteria that may cause cellulitis in such patients include Acinetobacter, Clostridium, Enterobacter, E. coli, Hemophilus, Pasteurella, Proteus, Pseudomonas and other forms of strep like group B or G.

Treatment of cellulitis involves the use of antibiotics. For patients without any medical issues an antibiotic with broad coverage against strep or staph is usually given. Typically, a form of penicillin or cephalosporin is given. For more severe infections the antibiotic may be given through an IV and hospitalization may be required. Antibiotics may be changed or added if no improvement is seen or if there is concern for a type of bacteria other than strep or staph causing the infection. Pain may be relieved with cool compresses and soaks. Elevation of the leg may expedite recovery from cellulitis affecting the leg. For patients who experience many episodes of cellulitis antibiotics may be given for months or years at a time.

Certain factors may play a role in the development of cellulitis and these factors may need to be treated in order to break the cellulitis cycle. Tinea of the toe webs, more commonly known as athlete’s foot, may set the skin up for recurrent cellulitis. The fungus of athlete’s foot damages the skin allowing bacteria to enter. Therefore, your doctor may stress the importance of treating athlete’s foot. Recurrent cellulitis has also been reported in those who have had leg veins removed for coronary artery bypass grafting (CABG).

Other Types of Cellulitis:

Facial Cellulitis
Facial cellulitis can occur in children and adults and can be a potentially serious ailment. Fever, irritability, swelling and redness begin abruptly over a day or two on the cheek. The infection is serous enough that it can spread to the meninges of the brain, causing meningitis.

Hemophilus type B Cellulitis
Hemophilus type B cellulitis develops after injury to the mouth or spreads from a middle ear infection (otitis media). Children between 6 months and 5 years of age were historically affected. A mother’s antibodies protect children younger than 6 months of age. However, the use of routine vaccination has made this type of cellulitis less common. Symptoms start after an upper respiratory infection (URI).

Fever sets in rapidly and can become quite high. The cheek becomes tender, warm and develop a red to purple color, a phenomenon known as “bruised cheek syndrome”. Meningitis may develop and a lumbar puncture may be performed to aid in the diagnosis. A culture taken from a sample of blood may grow the organism.

Cellulitis Around the Eye (Periorbital Cellulitis)
Periorbital cellulitis is an infection of the skin of the eyelids. Children are more likely to be affected. Often an initial sinusitis, URI or eye injury precedes the development of this type of cellulitis. There is rapid onset of warmth, redness and swelling of the eyelids and mucous membranes of the eye. Typically a patient maintains their ability to move the eye and look around.

Orbital Cellulitis
Orbital cellulitis is a medical emergency. This is a fairly uncommon disease. The signs and symptoms include drooping of the eyelid, inability to move the eye, and visual disturbances, like double vision. Sinusitis usually precedes this condition and the infection spreads directly from the sinuses or tracks backwards through veins of the face to infect the orbit or eye. Complications include abscess formation (collections or pockets of pus and infection), blindness, limited eye movement, and double vision. Rarer, but serious complications, include cavernous sinus thrombosis (a form of blood clot) and brain abscesses and even rarer, meningitis may develop.

Treatment includes hospitalization, IV antibiotics, imagining (like a CT scan), and vision exam. Some infections require a surgical intervention to decrease pressure and drain the infection.

Perianal Cellulitis
Perianal cellulitis typically occurs in children and is a cellulitis or infection of the skin surrounding the anus. The usual bacterium is a group A strep, the type that commonly causes strep throat. The skin around the anus appears bright red and may also be infected with a yeast like Candida. Associated symptoms include painful bowel movements, tenderness, itching, leakage of stool, stools that are tinged with blood. A sore throat may precede the development of perianal cellulitis. Other diseases that can cause a similar appearing rash are yeast (Candida) infection, psoriasis, pinworms, allergy, inflammatory bowel disease, seborrheic dermatitis and even child abuse. Cultures of the skin confirm the presence of the cellulitis.

Treatment includes an antibiotic to taken by mouth, which should also treat the strep throat if present. In addition, a topical antibiotic cream may be prescribed to apply to the rash to proved more rapid relief from the symptoms. The infection can recur and cultures should be performed again.

Pseudomonas Cellulitis
Pseudomonas cellulitis occurs as an infection localized to a specific area or as part of a more serious blood infection with Pseudomonas. Pseudomonas is a type of bacteria typically found in moist environments, like hot tubes and other types of water reservoirs. The localized form develops at sites of fungus infection, like athlete’s foot (Tinea pedis) or jock itch (Tinea cruris) as well as in bed sores, leg ulcers, burns, skin grafts, sites of traumatic injuries, and on penises of uncircumcised men. The skin in these areas is moist and has lost its protective barrier allowing the Pseudomonas to thrive and grow and gain access to the deeper skin.

The skin is dusky red in color. It may emit a fruity (grape) or “mousey” odor. Erosions develop as the skin is further broken down and dead (necrotic) skin accumulates. Blisters and pustules (pus filled bumps) can surround the area of infection. When a Pseudomonas septicemia (severe blood infection) exists, a deep, painful cellulitis may develop that can accumulate dead (necrotic) tissue. Treatment includes vinegar compresses and oral antibiotics. Severe skin infections and blood infections require IV antibiotics and hospitalization.


Habif, TP. Clinicial Dermatology a color guide to diagnosis and therapy, Mosby, Inc., 2004, p. 273-278, 292.

Angela Leo, D.O.
Department of Dermatology
Philadelphia College of Osteopathic Medicine/Frankford Hospital
Philadelphia, Pennsylvannia.