Cellulitis
Cellulitis is an inflammation of the connective tissue underlying the skin, that can be caused by a bacterial infection. Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, burns, insect bites, surgical wounds, or sites of intravenous catheter insertion.
Skin on the face or lower legs is most commonly affected by this infection, though cellulitis can occur on any part of the body. Cellulitis may be superficial — affecting only the surface of the skin — but cellulitis may also affect the tissues underlying the skin and can spread to the lymph nodes and bloodstream.
It is unrelated to cellulite, a cosmetic condition featuring dimpling of the skin.
A few of the forms of cellulitis are as follows: periorbital cellulitis (an infection of the eye socket), erysipelas, clostridial cellulitis, nonclostridial cellulitis, and synergistic necrotizing cellulitis (Pankey, 1992). A few forms of cellulitis do not have some of the symptoms most commonly listed (for example, clostridial and nonclostridial cellulitis do not cause the skin to turn red), but the majority do. Necrotizing fasciitis can be mistaken for cellulitis but is notable for involvement of the deeper tissue structures, the fascia, and can be limb and life threatening.
Cellulitis is caused by a type of bacteria entering by way of a break in the skin. This break need not be visible. Group A streptococcus and staphylococcus are the most common of these bacteria, which are part of the normal flora of the skin but cause no actual infection until the skin is broken. Predisposing conditions for cellulitis include insect bite, animal bite, pruritic skin rash, recent surgery, athlete's foot, dry skin, eczema, burns and boils, though there is debate as to whether minor foot lesions contribute.
The appearance of the skin will help a doctor make a diagnosis. The doctor may also suggest blood tests, a wound culture or other tests to help rule out a blood clot deep in the veins of the legs. Cellulitis in the lower leg is characterized by signs and symptoms that may be similar to those of a clot occurring deep in the veins, such as warmth, pain and swelling.
This reddened skin or rash may signal a deeper, more serious infection of the inner layers of skin. Once below the skin, the bacteria can spread rapidly, entering the lymph nodes and the bloodstream and spreading throughout the body.
In rare cases, the infection can spread to the deep layer of tissue called the fascial lining. Necrotizing fasciitis, also called by the media "flesh-eating bacteria", is an example of a deep-layer infection. It represents an extreme medical emergency.