What is cellulitis? Cellulitis is a bacterial infection that typically affects the skin and the tissues beneath the skin. Cellulitis can occur anywhere on the body. Periorbital cellulitis (infection of the eyelids or other soft tissue around the eyes) is a particularly serious form of cellulitis. Cellulitis is most frequently caused by the bacteria Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus, or MRSA), Streptococcus pneumoniae, and beta-hemolytic streptococci. Whenever the offending bacteria enter through a break in the skin—for example, from an injury or insect bite, or through a disorder that breaks the skin, such as cracks or peeling from dry skin, a stye, or a hordeolum (localized bacterial infection of an oil gland or eyelash follicle in the eyelid margin)—they can quickly lead to inflammation and infection. Cellulitis can be serious and sometimes requires hospitalization; however, in many people, cellulitis responds promptly to antibiotic therapy. The infection can be harder to eliminate in people who have chronic medical conditions, especially conditions that suppress the immune system. Orbital cellulitis (invasive infection of the soft tissues around the eye) is particularly dangerous for everyone, but especially for children. The infection can advance rapidly and in some cases may cause blindness or other life-threatening complications. Seek immediate medical care (call 911) if you, or someone you are with, have signs of cellulitis on your face, particularly near your eyes, including painful red, warm or inflamed skin, a rash or sore that appears suddenly and grows rapidly within 24 hours; tight, or a glossy appearance to the inflamed area. Also, seek immediate medical care (call 911) if you, or someone you are with, have serious symptoms of sepsis (a life-threatening bacterial blood infection), such as severe difficulty breathing and sweating, which may be combined with high fever (higher than 101 degrees Fahrenheit), pale or blue lips, and rapid heart rate (tachycardia). Seek prompt medical care if you are being treated for cellulitis but your symptoms recur or persist.