Most cases of erysipelas are due to Streptococcus pyogenes (also known as beta-hemolytic group A streptococci), although non-group A streptococci can also be the causative agent. Beta-hemolytic, non-group A streptococci include Streptococcus agalactiae, also known as group B strep or GBS. Historically, the face was most affected; today, the legs are affected most often.[3] The rash is due to an exotoxin, not the Streptococcus bacteria, and is found in areas where no symptoms are present; e.g., the infection may be in the nasopharynx, but the rash is found usually on the upper dermis and superficial lymphatics.
Erysipelas infections can enter the skin through minor trauma, insect bites, dog bites, eczema, athlete's foot, surgical incisions and ulcers and often originate from streptococci bacteria in the subject's own nasal passages. Infection sets in after a small scratch or abrasion spreads, resulting in toxaemia.
Erysipelas does not affect subcutaneous tissue. It does not release pus, only serum or serous fluid. Subcutaneous edema may lead the physician to misdiagnose it as cellulitis, but the style of the rash is much more well circumscribed and sharply marginated than the rash of cellulitis.
Risk factors[edit] => This disease is most common among the elderly, infants, and children. People with immune deficiency, diabetes, alcoholism, skin ulceration, fungal infections, and impaired lymphatic drainage (e.g., after mastectomy, pelvic surgery, bypass grafting) are also at increased risk.
This disease is diagnosed mainly by the appearance of well-demarcated rash and inflammation. Blood cultures are unreliable for diagnosis of the disease, but may be used to test for sepsis. Erysipelas must be differentiated from herpes zoster, angioedema, contact dermatitis, and diffuse inflammatory carcinoma of the breast.
Erysipelas can be distinguished from cellulitis by its raised advancing edges and sharp borders. Elevation of the antistreptolysin O titer occurs after around 10 days of illness.
Affected individuals typically develop symptoms including high fevers, shaking, chills, fatigue, headaches, vomiting, and general illness within 48 hours of the initial infection. The erythematous skin lesion enlarges rapidly and has a sharply demarcated, raised edge. It appears as a red, swollen, warm, and painful rash, similar in consistency to an orange peel. More severe infections can result in vesicles (pox or insect bite-like marks), blisters, and petechiae (small purple or red spots), with possible skin necrosis (death). Lymph nodes may be swollen, and lymphedema may occur. Occasionally, a red streak extending to the lymph node can be seen.
The infection may occur on any part of the skin, including the face, arms, fingers, legs, and toes; it tends to favour the extremities. Fat tissue and facial areas, typically around the eyes, ears, and cheeks, are most susceptible to infection. Repeated infection of the extremities can lead to chronic swelling (lymphangitis).