Cellulitis is a spreading bacterial infection just below the skin surface. It is most commonly caused by Streptococcus pyogenes or Staphylococcus aureus.
The word "cellulitis" actually means "inflammation of the cells." Specifically, cellulitis refers to an infection of the tissue just below the skin surface. In humans, the skin and the tissues under the skin are the most common locations for microbial infection. Skin is the first defense against invading bacteria and other microbes. An infection can occur when this normally strong barrier is damaged due to surgery, injury, or a burn. Even something as small as a scratch or an insect bite allows bacteria to enter the skin, which may lead to an infection. Usually, the immune system kills any invading bacteria, but sometimes the bacteria are able to grow and cause an infection.
Once past the skin surface, the warmth, moisture, and nutrients allow bacteria to grow rapidly. Disease-causing bacteria release proteins called enzymes which cause tissue damage. The body's reaction to damage is inflammation which is characterized by pain
, redness, heat, and swelling. This red, painful region grows bigger as the infection and resulting tissue damage spread. An untreated infection may spread to the lymphatic system (acute lymphangitis
), the lymph nodes (lymphadenitis
), the bloodstream (bacteremia
), or into deeper tissues. Cellulitis most often occurs on the face, neck, and legs.
A very serious infection, called orbital cellulitis, occurs when bacteria enter and infect the tissues surrounding the eye. In 50-70% of all cases of orbital cellulitis, the infection spreads to the eye(s) from the sinuses or the upper respiratory tract (nose and throat). Twenty-five percent of orbital infections occur after surgery on the face. Other sources of orbital infection include a direct infection from an eye injury, from a dental or throat infection, and through the bloodstream.
Infection of the tissues surrounding the eye causes redness, swollen eyelids, severe pain, and causes the eye to bulge out. This serious infection can lead to a temporary loss of vision, blindness, brain abscesses, inflammation of the brain and spinal tissues (meningitis
), and other complications. Before the discovery of antibiotics
, orbital cellulitis caused blindness in 20% of patients and death
in 17% of patients. Antibiotic treatment has significantly reduced the incidence of blindness and death.
Causes and symptoms
Although other kinds of bacteria can cause cellulitis, it is most often caused by Streptococcus pyogenes
(the bacteria which causes strep throat
) and Staphylococcus aureus. Streptococcus pyogenes
is the so-called "flesh-eating bacteria" and, in rare cases, can cause a dangerous, deep skin infection called necrotizing fasciitis. Orbital cellulitis may be caused by bacteria which cannot grow in the presence of oxygen (anaerobic bacteria). In children, Haemophilus influenzae
type B frequently causes orbital cellulitis following a sinus infection.
can be picked up from a person who has strep throat or an infected sore. Other cellulitis-causing bacteria can be acquired from direct contact with infected sores. Persons who are at a higher risk for cellulitis are those who have a severe underlying disease (such as cancer
, diabetes, and kidney disease
), are taking steroid medications, have a reduced immune system (because of AIDS
, organ transplant, etc.), have been burned, have insect bites, have reduced blood circulation to limbs, or have had a leg vein removed for coronary bypass surgery. In addition, chicken pox, human or animal bite wounds
, skin wounds, and recent surgery can put a person at a higher risk for cellulitis.
The characteristic symptoms of cellulitis are redness, warmth, pain, and swelling. The infected area appears as a red patch that gets larger rapidly within the first 24 hours. A thick red line which progresses towards the heart may appear indicating an infection of the lymph vessels (lymphangitis). Other symptoms which may occur include fever
, chills, tiredness, muscle aches, and a general ill feeling. Some people also experience nausea, vomiting, stiff joints, and hair loss at the infection site.
The characteristic symptoms of orbital cellulitis are eye pain, redness, swelling, warmth, and tenderness. The eye may bulge out and it may be difficult or impossible to move. Temporary loss of vision, pus drainage from the eye, chills, fever, headaches, vomiting, and a general ill feeling may occur.
Cellulitis may be diagnosed and treated by a family doctor, an infectious disease specialist, a doctor who specializes in skin diseases (dermatologist), or in the case of orbital cellulitis, an eye doctor (ophthalmologist). The diagnosis of cellulitis is based mainly on the patient's symptoms. The patient's recent medical history is also used in the diagnosis.
Laboratory tests may be done to determine which kind of bacteria is causing the infection but these tests are not always successful. If the skin injury is visible, a sterile cotton swab is used to pick up a sample from the wound. If there is no obvious skin injury, a needle may be used to inject a small amount of sterile salt solution into the infected skin, and then the solution is withdrawn. The salt solution should pick up some of the bacteria causing the infection. A blood sample may be taken from the patient's arm to see if bacteria have entered the bloodstream. Also, a blood test may be done to count the number of white blood cells in the blood. High numbers of white blood cells suggest that the body is trying to fight a bacterial infection.
For orbital cellulitis, the doctor may often perform a special x-ray scan called computed tomography scan (CT). This scan enables the doctor to see the patient's head in cross-section to determine exactly where the infection is and see if any damage has occurred. A CT scan takes about 20 minutes.
Antibiotic treatment is the only way to battle this potentially life-threatening infection. Mild to moderate cellulitis can be treated with the following antibiotics taken every four to eight hours by mouth:
- penicillins (Bicillin, Wycillin, Pen Vee, V-Cillin)
- erythromycin (E-Mycin, Ery-Tab)
- cephalexin (Biocef, Keflex)
- cloxacillin (Tegopen)
Other medications may be recommended, such as acetaminophen
(Tylenol) or ibuprofen (Motrin, Advil) to relieve pain, and aspirin
to decrease fever.
A normally healthy person is usually not hospitalized for mild or moderate cellulitis. General treatment measures include elevation of the infected area, rest, and application of warm, moist compresses to the infected area. The doctor will want to see the patient again to make sure that the antibiotic treatment is effective in stopping the infection.
Persons at high risk for severe cellulitis will probably be hospitalized for treatment and monitoring. Antibiotics may be given intravenously to patients with severe cellulitis. Complications such as deep infection, or bone or joint infections, might require surgical drainage and a longer course of antibiotic treatment. Extensive tissue destruction may require plastic surgery to repair. In cases of orbital cellulitis caused by a sinus infection, surgery may be required to drain the sinuses.
Over 90% of all cellulitis cases are cured after seven to ten days of antibiotic treatment. Persons with serious disease and/or those who are taking immunosuppressive drugs may experience a more severe form of cellulitis which can be life threatening. Serious complications include blood poisoning
(bacteria growing in the blood stream), meningitis (brain and spinal cord infection), tissue death (necrosis), and/or lymphangitis (infection of the lymph vessels). Severe cellulitis caused by Streptococcus pyogenes
can lead to destructive and life-threatening necrotizing fasciitis.
— A local, protective response to tissue injury. It is characterized by redness, warmth, swelling, and pain.
— A destructive infection which follows severe cellulitis and involves the deep skin and underlying tissues.
— Air cavities found in the bones of the head. The sinuses which are connected to the nose are prone to infection.
Cellulitis may be prevented by wearing appropriate protective equipment during work and sports to avoid skin injury, cleaning cuts and skin injuries with antiseptic soap, keeping wounds clean and protected, watching wounds for signs of infection, taking the entire prescribed dose of antibiotic, and maintaining good general health. Persons with diabetes should try to maintain good blood sugar control.
Lewis, Ronald T. "Soft Tissue Infections." World Journal of Surgery 22, no. 2 (February 1998): 146-51.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
cellulitis (sel?yu-lit'is ) [ cellula + -itis, ]
A spreading bacterial infection of the skin and subcutaneous tissues, usually caused by streptococcal or staphylococcal infections in adults (and occasionally by Haemophilus
species in children). It may occur following damage to skin from an insect bite, an excoriation, or other wound. The extremities, esp. the lower legs, are the most common sites. Adjacent soft tissue may be involved. Affected skin becomes inflamed: red, swollen, warm to the touch, and tender. Spread of infection up lymphatic channels may occur. Cellulitis involving the face is called erysipelas. When it affects the lower extremities, cellulitis must be differentiated from stasis dermatitis, which is associated most commonly with bilateral, chronic dependent edema and, occasionally, with deep venous thrombosis. Risk factors for cellulitis include diabetes mellitus, lymphedema, venous stasis or insufficiency, immune suppression, injection drug use, malnutrition, peripheral vascular disease, and previous skin diseases. See: illustration
; necrotizing fasciitis
Bacteria gain access through breaks in the skin and spread rapidly, overwhelming normal body defenses; lesions between the toes from athlete's foot are common entry sites.
For mild cases of cellulitis, oral antibiotics may be effective depending on the causative organism. For severe cases, intravenous penicillinase-resistant penicillins are used; surgical débridement to obtain cultures and to rule out fasciitis is recommended for patients with diabetes.
Rarely, group A streptococcal cellulitis may be complicated by exfoliative dermatitis or infection of the subcutaneous fat and fascia, causing necrosis (necrotizing fasciitis), a condition popularly ascribed to the action of “flesh-eating bacteria.”
Blood cultures should be obtained from patients with cellulitis to assess for sepsis before beginning therapy with antibiotics. The affected body part should be elevated above the level of the heart. Outlining the affected area with a skin marker allows the caregiver to readily determine if inflamed tissues are responding to therapy. Size, shape, color, and temperature of the affected area and surrounding tissues should be documented and any drainage described. Applying warm soaks to the area increases vasodilation, thus decreasing edema and relieving pain. Pain should be treated with prescribed oral analgesics and anti-inflammatory drugs. Blood sugars, if elevated, should be lowered to normal levels (preferably about 126 mg/dl or less). Patients on prolonged bedrest should be given heparin to prevent deep venous thrombosis as well as stool softeners to prevent constipation. Patients who develop cellulitis are often at risk for recurrence; they should learn general skin hygiene, how to clean cuts, scratches, cracked skin, and abrasions, and the importance of prompt treatment for infections.
dissecting cellulitis of the scalp
An inflammatory pustular disease of the scalp, similar to acne conglobata or hidradenitis suppurativa. It can be treated surgically, with isotretinoin, or with laser therapy. Synonym: perifolliculitis capitis abscedens
A rash marked by firm, swollen, itchy patches that appear suddenly. The patches may be oval or circular, violet or red, and are associated with abnormally high blood eosinophil levels. The cause is unknown. Synonym: Wells syndrome
orbital cellulitisPostseptal cellulitis.
periorbital cellulitisPreseptal cellulitis.
Facial infection invading the orbit. Synonym: orbital cellulitis
Soft tissue infection limited to the tissues anterior to the orbital septum. Synonym: periorbital cellulitisillustrationillustration
Medical Dictionary, © 2009 Farlex and Partners
Patient discussion about cellulitis
Q. What is Cellulitis? I am a bit overweight and have cellulite, does this mean I have Cellulitis?
A. Cellulite is a dimpled appearance to your skin. It is harmless. Whereas, Cellulitis is a common, potentially serious bacterial skin infection. Cellulitis appears as a swollen, red area of skin that feels hot and tender, and it may spread rapidly. Skin on lower legs is most commonly affected, though cellulitis can occur anywhere on your body or face. Cellulitis canalso affect tissues underlying the skin and can spread to the lymph nodes and bloodstream. If it is left untreated, it can spread and become life-threatening.
Q. How to treat cellulitis? My Mother is 73 and has been diagnosed with cellulitis on her leg. She is in a lot of pain. What is the most effective treatment for it?
A. Here is a movie with tips on managing cellulitis:
Q. Is Diabetes a risk factor for developing cellulitis? I am 50 years old and have type 2 diabetes. Is it true that diabetes can cause cellulitis? if so, what can be done to prevent it?
A. To help prevent cellulitis and other infections, follow these measures anytime you have a skin wound: More discussions about cellulitis
Wash your wound daily with soap and water.
Apply an antibiotic cream or ointment. Cover your wound with a bandage. Change bandages often. Change them at least daily or whenever the bandage becomes wet or dirty.
Watch for signs of infection. Redness, pain and drainage all signal possible infection and the need for medical evaluation.
People with diabetes and those with poor circulation need to take extra precautions to prevent skin wounds and treat any cuts or cracks in the skin promptly. Good skin-care measures include the following:
Moisturize your skin regularly.
Trim your fingernails and toenails carefully.
Protect your hands and feet. Promptly treat any superficial skin infections, such as athlete's foot.
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