Cellulitis is an inflammation due to bacterial infection of the deep layers of the skin (the deep dermis and subcutaneous tissue). It can also spread to tissues underneath the skin or to the blood and lymph nodes.

The bacteria that cause cellulitis can enter the body through a cut, puncture wound or after surgery. Some risk factors for cellulitis include age, diabetes and alcoholism.

Cellulitis can occur on any part of the body, but it is most common on the legs and face. It differs from impetigo, which is a more superficial skin infection.

There are several types of cellulitis including preseptal cellulitis (inflammation of the eyelid), necrotizing cellulitis (a severe form of cellulitis characterized by death of infected tissue) and erysipelas (bacterial infection of the skin and tissue below the skin that affects the face, ears and lower legs).

Symptoms of cellulitis include a general sick feeling (malaise), red and inflamed skin and pain or tenderness in the affected area. Patients experiencing severe symptoms such as a high fever, significant pain or the inability to move a limb due to pain should seek immediate medical attention. 

Cellulitis is usually treated with antibiotics (medications that kill or slow the growth of harmful microorganisms, such as bacteria). They are usually taken orally. Symptoms typically disappear within a few days of starting the medication. Patients that do not respond to the initial treatment or have severe symptoms may require hospitalization and intravenous administration of antibiotics.

To prevent cellulitis, patients should wear protective equipment during work or sports to prevent breaks in the skin. Those with existing skin wounds should keep them clean and covered to avoid infection.

Cellulitis is an acute inflammation of the deeper layers of the skin caused by a bacterial infection.

The skin is composed of three layers:

• Epidermis. Protective outer layer of the skin.
  
  
• Dermis. The middle layer of the skin, below the epidermis and above the subcutaneous tissue. It is composed of connective tissue which contains hair follicles, sweat glands, blood vessels and nerve fibers.
  
  
• Subcutaneous tissue. The deepest layer of skin, under the epidermis and dermis. Subcutaneous tissue is composed of fat, tissue that separates the fat in pockets, nerves and blood vessels.

Bacteria may gain access to the dermis via an external route or via a blood-borne route.

Under normal circumstances, the skin has many different types of bacteria living on it. In most cases, the epidermis prevents bacteria from getting inside the body. If the skin is broken from a cut or other means, bacteria have the opportunity to enter and grow in the body, causing infection and inflammation.

Cellulitis occurs when the deep dermis and subcutaneous tissue of the skin become infected. It can occur on any area of the body. However, children usually develop cellulitis on the face and neck, and adults develop it more often on their extremities.  

When infected, the skin tissues become red, hot, irritated and painful. The infection may only impact the skin, or it may affect other tissues and spread to the lymph nodes and blood. Fluid-filled blisters sometimes develop.

Cellulitis is different from impetigo, a bacterial skin infection generally limited to the epidermis.

In healthy people, cellulitis rarely poses serious problems. However, if untreated or not treated properly, it can lead to complications, including:

• Gangrene (tissue death) of affected areas.
  
  
• Infections and shock (a life-threatening condition characterized by the body’s inability to supply enough oxygen to meet tissue requirements).
  
  
• Meningitis (inflammation of the membrane surrounding the brain and spinal cord) may develop if cellulitis occurs on the face.
  
  
• Lymphangitis (inflammation of the lymph vessels).
  
  
• Lymphadenitis (inflammation of the lymph nodes).
  
  
• Acute glomerulonephritis (kidney inflammation).
  
  
• Subacute bacterial endocarditis (heart inflammation).

Cellulitis is a bacterial infection of the skin that can occur anywhere in the body. There are several distinct types of cellulitis. They include:

• Preseptal cellulitis. Infection of the eyelid and soft tissues around the eye socket, which causes redness and swelling of the eyelid. It commonly occurs after trauma to the eyelid or when an infection in the upper respiratory tract spreads to the eye. It occurs more frequently in children.
  
  
• Orbital cellulitis. Similar to preseptal cellulitis, it affects tissue around the eye socket. This type is often a complication of sinusitis (sinus infection), and occurs more often in children.
  
  
• Necrotizing cellulitis. A severe form of cellulitis characterized by death of infected tissue (necrosis). Some bacterial infections can cause small blood vessels in the infected area to clot, causing the tissue served by the vessels to die from a lack of blood. When this happens, the immune defenses (such as white blood cells and antibodies) cannot reach the dead tissue. The infection spreads rapidly and sometimes leads to death if not treated.
  
  
• Erysipelas. An acute superficial form of cellulitis that is usually caused by a group A streptococci bacteria infection. It is characterized by hot, red, swollen and sharply defined skin eruption.

Cellulitis occurs when one or more types of bacteria enter the body. The most common types of bacteria that cause cellulitis include streptococcus and staphylococcus.

There are many injuries and conditions that can cause bacteria to enter the body and lead to cellulitis. They include:

• Cuts or scrapes
  
  
• Puncture wounds (including body piercings)
  
  
• Burns
  
  
• Ischemic ulcers (non-healing sores on the hands and feet)
  
  
• Athlete’s foot (contagious infection of the feet caused by fungi)
  
  
• Skin disorders, such as dermatitis
  
  

  

• Surgery
  
  
• Certain types of insect and spider bites
  
  
• Animal or human bites
  
  
• Areas of dry, flaky skin
  
  
• Chickenpox and shingles (common viral diseases that cause blisters on the skin)

There is increased risk for cellulitis if there are breaks in the skin barrier when handling fish, shellfish, poultry, eggs or meat. The bacteria that reside normally on fish, poultry or livestock are not common to humans and can infect the skin through an open wound.

Other conditions and diseases that increase the risk of developing cellulitis include:

• Recent heart, lung, dental or other procedures
  
  
• Use of corticosteroids
  
  
• Alcoholism
  
  
• Diabetes
  
  
• Intravenous drug abuse
  
  
• Peripheral vascular disease (disease of the blood vessels outside the heart and brain)
  
  
• Poor circulation or heart failure
  
  
• Lymphedema (chronic swelling of the arms and legs)

Age also affects a person’s risk for developing cellulitis. As people age, their circulatory system becomes less efficient at delivering blood. Since blood contains infection-fighting white blood cells, poor circulation may lead to cellulitis, as well as other infections.

People with a compromised immune system are also more likely to develop the condition. This group includes AIDS patients, cancer patients and those taking certain immunosuppressants.

Many patients with cellulitis experience a general ill feeling (malaise). Other common symptoms include:

• Skin redness or inflammation that may spread as the infection spreads
  
  
• Tight, glossy or stretched appearance of the skin
  
  
• Pain or tenderness in the affected area
  
  
• Skin lesions or rashes that may develop suddenly and grow rapidly with ill-defined borders
  
  
• Warmth over the area of redness
  
  
• Chills, fever or shaking
  
  
• Fatigue
  
  
• Muscle aches and pains, including joint stiffness
  
  
• Nausea and vomiting
  
  
• Hair loss at the site of the infection
  
  
• Blurred vision (when cellulitis affects the eye)
  
  
• Swollen lymph nodes
  
  
• Fluid drainage from the affected skin

Depending on the type of bacteria causing the condition, symptoms of cellulitis may appear anywhere from four hours to several days after the infection develops.

Patients who suspect that they have developed cellulitis are encouraged to contact their physician. Left untreated, the condition can lead to serious health problems.  

Patients should seek immediate medical attention if they are experiencing any of the following symptoms because it may indicate that the infection has spread or poses a serious health risk:

• Fever over 100 degrees Fahrenheit (38 degrees Celsius), especially if chills are also present.
  
  
• A red streak from the affected area of the skin. This may indicate that a different medication is needed or the infection has spread.
  
  
• Significant pain not relieved by over-the-counter pain medications.
  
  
• Inability to move a limb or joint because of pain.

Cellulitis is usually diagnosed by a physician during a physical examination. The physician will collect the patient’s medical history including a list of current medications. During the exam, physicians may visually inspect the skin to detect the presence of swelling and redness. Some patients may have swollen glands (lymph nodes) near the affected area.

Physicians may perform the following tests, particularly if a patient is seriously ill:

• Complete blood count (CBC). A routine blood test that measures the composition of blood cells within the blood. This may reveal an elevated level of white blood cells, which indicates the presence of infection.
  
  
• Blood culture. A test that detects bacteria in the blood. It may be performed if it is suspected that the infection has spread.

X-rays and bone scans may be used to determine if the infection has developed under the skin or has spread to the bone. The physician may also perform other tests, including tests to differentiate cellulitis from deep vein thrombosis (blood clot in the deep veins of the leg) which causes similar symptoms to cellulitis in the leg.

Treatment for cellulitis involves killing the infecting bacteria and easing discomfort. Patients with mild symptoms are usually prescribed antibiotics, which are taken orally and administered for seven to 10 days. Symptoms usually disappear within a few days of taking medication. However, sometimes symptoms get worse before they get better due to the release of substances that cause tissue damage when bacteria are killed. When this occurs, the body continues to produce symptoms even though the bacteria are dead. Patients should take all prescribed medication, even after their symptoms disappear. This will allow complete clearance of the bacteria and help prevent the infection from returning.

In addition to taking medications, patients may be encouraged to elevate the infected area, usually higher than the heart, to minimize swelling. Applying warm compresses to the affected skin may also provide relief. Over-the-counter analgesics (pain medication) may be taken to alleviate pain as well. Patients with abscesses (collections of pus resulting from an infection) may need to have the pus drained from the wound by a physician.

The skin may flake or peel as it heals. In order to prevent additional injury to the skin, patients should avoid squeezing, rubbing, scratching or puncturing the affected skin during the healing process.

Patients with symptoms that are extensive, involve the eye (e.g., orbital cellulitis), do not clear up with antibiotics, or are accompanied by high fever may be hospitalized so the condition can be more closely monitored. Antibiotics may be administered through a vein (intravenously). Patients that have tissue death (necrotizing cellulitis) may require surgery to remove the infected tissue.

To help prevent breaks in the skin that can lead to cellulitis, protective clothing and equipment (e.g., knee pads, elbow pads, helmets, shin guards) should be worn during work activities and sports. Long sleeve shirts and pants should also be worn to protect the skin from injury during certain leisure activities (e.g., gardening, hiking).  

Patients with skin wounds can treat them properly to avoid infection. Some wound care tips include:

• Wash the wound daily with soap and water to keep it clean.
  
  
• Apply an antibiotic cream or ointment to the wound to prevent infection.
  
  
• Cover the wound with a bandage to keep it clean and prevent bacteria from entering. Change bandages often.
  
  
• Monitor for signs of infection, including redness and pain.
  
  
• Seek immediate medical attention for deep cuts or puncture wounds, large wounds and bites.

People with poor circulation, diabetes or other diseases that weaken the immune system and increase the risk of cellulitis may benefit from:

• Moisturizing skin frequently to prevent cracking and peeling.
  
  
• Trimming the fingernails and toenails carefully so that surrounding skin does not get injured.
  
  
• Protecting the hands and feet by wearing proper footwear and gloves.
  
  
• Treating skin infections, such as athlete’s foot, promptly to prevent the infection from spreading.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following cellulitis–related questions:

1. Do my symptoms suggest that I have cellulitis?
   
   
2. What methods will you use to determine if I have cellulitis?
   
   
3. Does cellulitis pose a danger to my overall health?
   
   
4. What may have caused me to develop cellulitis?
   
   
5. What are my treatment options?
   
   
6. When can I expect the condition to improve?
   
   
7. Will I require hospitalization?
   
   
8. What are my chances of developing cellulitis again in the future?
   
   
9. What steps can I take to prevent cellulitis?
   
   
10. For what cellulitis-related symptoms should I seek immediate medical attention?