Cellulitis is an infection of the skin and soft tissues, typically due to bacteria. It begins with red, tender, swollen area of skin. It can spread into the blood and lymph nodes and cause sepsis, a severe infection of the entire body. It is important to seek medical attention when the first signs are present. Typically, early infections can be treated with oral antibiotics. If the infection worsens, intravenous (or medicine into your bloodstream) antibiotics may be necessary and patients may have to stay in the hospital to be monitored.