Cellulitis is a spreading bacterial infection that occurs in the skin and subcutaneous tissue. The local skin may be red and feel painful as well as tender. Some patients may have fever, chills and other more severe symptoms. Antibiotics are needed to treat the infection. Cellulitis can be caused by a variety of bacteria, the most common of which is streptococcus. Streptococcus infections can spread rapidly through the skin because of its ability to produce an enzyme that limits the ability of tissues to fight infection. Staphylococcus can also cause cellulitis, and many other bacteria can also cause it, especially after human or animal bites, or injuries in water or mud. Bacteria usually invade through small breaks in the skin caused by superficial abrasions, punctures, burns, and skin diseases. Skin that is edematous is particularly susceptible to infection. Cellulitis is more common in people with poor circulation (chronic vascular insufficiency). Of course, cellulitis can also occur in areas of the skin that are not visibly damaged. Cellulitis is most common in the legs, but can occur anywhere on the body. The initial symptoms are flushing of the skin, pain, and localized tenderness. These symptoms are caused by both the bacteria themselves and the body’s attempt to fight off the infection. The affected area of skin becomes warm, swollen and appears slightly depressed, with an orange peel appearance. Sometimes filled blisters, which can be large or small, may appear. The affected area is usually poorly defined, except for the dermatitis type of cellulitis. Most patients with cellulitis have only mild discomfort, but some may have fever, chills, rapid heart rate, headache, hypotension, and confusion. As the infection spreads, nearby lymph nodes may become enlarged and painful to the touch (lymphadenitis), and lymphangitis may occur (lymphangitis). Sometimes the bacteria spread through the bloodstream (bacteremia), which can cause more severe systemic symptoms. When cellulitis occurs repeatedly in the same area, especially in the legs, the lymphatic vessels may be damaged, resulting in persistent swelling of the affected tissue. Physicians often diagnose cellulitis based on disease presentation and symptoms. Laboratory strain identification of blood, pus, or tissue specimens is usually not necessary unless the patient is very ill or does not respond to drug therapy. Because of the similarity to the symptoms of deep vein thrombosis, a physician’s examination is sometimes required to differentiate it from deep vein thrombosis (DVT) of the legs. Aggressive antibiotic therapy is effective in stopping the rapid spread of infection and allowing the drugs to reach the blood and internal organs. Antibiotics such as dicloxacillin or cefadroxil are effective against both streptococci and staphylococci. Oral antibiotics can be given to patients with mild cellulitis. In contrast, intravenous antibiotics are usually used for patients with rapidly spreading cellulitis, high fever, or signs of severe infection. If possible, the affected area of the body should be kept braked and elevated to help reduce swelling. Cold, moist compresses on the affected skin can relieve discomfort. Symptoms of cellulitis usually resolve after a few days of antibiotic treatment. However, symptoms often worsen before they get better and may be related to the death of the bacteria releasing substances that cause tissue damage. When this occurs, the body continues to react despite the death of the bacteria. Even if the symptoms disappear earlier, antibiotic treatment still needs to be continued for more than 10 days.