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Cellulitis: Causes, Symptoms and Treatment

Cellulitis is an acute spreading inflammation of the deeper layers of the skin caused by a bacterial infection and it can occur anywhere in the body.

The skin is composed of the protective outer layer called epidermis, the middle layer called dermis and subcutaneous tissue which is the deepest layer of the skin. Bacteria may gain access to the dermis via an external route or a blood-borne route. The role of epidermis is to prevent bacteria from getting inside the body. However, if the skin is broken from a cut or surgery wound, harmful bacteria can enter and grow in the body, causing infection and inflammation.

When the deep dermis and subcutaneous tissue of the skin become infected with bacteria, cellulitis occurs. Although cellulitis can occur on any area of the body, children usually develop infection on their face and neck whereas adults develop it more often on their extremities. Infected skin usually becomes red, hot and painful. The infection may also affect other tissues and spread to the lymph nodes and blood. In some cases, fluid-filled blisters develop. Cellulitis should not be confused with impetigo, a contagious bacterial skin infection largely limited to the epidermis.

Cellulitis rarely poses serious health problems in otherwise healthy people. However, if left untreated, it can lead to more serious complications, including further infections, gangrene, meningitis (if cellulitis occurs on the face), lymphadenitis, lymphangitis, acute glomerulonephritis and subacute bacterial endocarditis.

Types of Cellulitis

Preseptal cellulitis is the infection of the eyelid and soft tissues around the eye socket, causing redness and swelling of the eyelid. This type of cellulitis occurs more often in children.

Orbital cellulitis is similar to preseptal cellulitis in that it affects tissue around the eye socket. Orbital cellulitis is often a complication of sinus infection and occurs more frequently in children.

Necrotizing cellulitis is a severe form of rapidly spreading cellulitis infection characterized by death of infected tissue. Clotting of small blood vessels in the infected area causes the tissue served by the vessels to die from a lack of blood. When it happens, the immune defenses cannot reach the dead tissue. If not treated, necrotizing cellulitis may sometimes lead to death.

Erysipelas is an acute superficial form of cellulitis usually caused by a group A streptococci bacterial infection. This type of cellulitis is characterized by red, hot, swollen and sharply defined skin eruptions.

Causes and Risk Factors for Cellulitis

The most common types of bacteria that tend to cause cellulitis include streptococcus and staphylococcus. Conditions and injuries that can cause such bacteria to enter the body and lead to cellulitis include:

  • Cuts, stings or scrapes
  • Puncture wounds (e.g., from body piercings)
  • Surgery wounds
  • Burns
  • Insect or animal bites
  • Ischemic ulcers
  • Athlete’s foot
  • Skin disorders, e.g., dermatitis
  • Chickenpox and shingles
  • Areas of dry, flaky skin

People handling fish, shellfish, meat, poultry and eggs are at an increased risk for contracting cellulitis. The bacteria that normally reside on fish, livestock and poultry are not common to humans and can infect the skin through cuts or scrapes.

Other conditions that increase the risk of contracting cellulitis include:

  • Diabetes
  • Recent dental, lung, heart or other procedures
  • Use of corticosteroids
  • Alcoholism
  • Intravenous drug abuse
  • Lymphedema
  • Poor blood circulation or heart failure
  • Peripheral vascular disease
  • Compromised immune system
  • High age

Symptoms of Cellulitis

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

Depending on the type of bacteria, symptoms may appear anywhere from four hours to several days after the infection develops. Patients should seek immediate medical attention if any of the following symptoms of cellulitis occur:

  • Fever over 38 degrees Celsius (100 degrees Fahrenheit), especially if chills are also present.
  • A red streak from the affected area of the skin.
  • Inability to move a limb or joint because of pain.
  • Significant pain not relieved by common over-the-counter pain medications.

Diagnosing Cellulitis

To diagnose cellulitis, the physician will visually inspect the skin to detect the presence of redness and swelling. Some patients may have swollen glands near the affected area.

The following tests are usually performed:

  • Complete blood count (CBC) to determine the presence of infection.
  • Blood culture to detect bacteria in the blood.
  • X-rays and bone scans may be ordered to determine if the infection has developed under the skin or has spread to the bone.

Other tests that may be required include tests to distinguish cellulitis from deep vein thrombosis which has similar symptoms to those of cellulitis in the leg.

Treatment of Cellulitis

Cellulitis treatment consists in killing the infecting bacteria and easing discomfort. For mild symptoms, oral antibiotics are usually prescribed and administered for seven to ten days. Symptoms typically disappear within a few days of taking antibiotics. However, in some cases symptoms can get worse before they get better. This is due to the release of substances causing tissue damage when bacteria are killed. When this happens, the body continues to produce symptoms even though the bacteria are dead. Common over-the-counter pain medication may be taken to alleviate pain.

Besides taking medications, patients may be urged to elevate the infected area higher than the heart to reduce swelling. Applying warm compresses to the affected area of the skin should also provide relief. Patients who develop abscesses may need to have the pus drained from the wound by a physician. The skin may flake or peel as it heals. Patients should avoid rubbing, scratching or squeezing the affected skin during the healing process to prevent additional skin injury.

Patients with serious extensive symptoms, symptoms that involve the eye, do not clear up with medication or are accompanied by high fever may need to be hospitalized to monitor the condition more closely. If necessary, antibiotics may also be administered intravenously. Patients with necrotizing cellulitis may require surgery to remove the infected tissue.

Prevention of Cellulitis

To help prevent infection, people should wear protective clothing and equipment during work activities and sports to avoid breaks in the skin and other injuries that can lead to cellulitis. People with existing skin wounds should treat and cover them properly to prevent possible infection. Patients with diabetes, poor circulation or other conditions that weaken the immune system and increase the risk of cellulitis should be particularly careful to avoid skin cuts and injuries and, if they happen, keep them clean and treat them correctly.

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