<unk>  is usually diagnosed by the clinician looking at the characteristic well-demarcated rash following a history of injury or recognition of one of the risk factors. Tests, if performed, may show a high white cell count, raised CRP or positive blood culture identifying the organism.<unk>  must be differentiated from herpes zoster, angioedema, contact dermatitis, erythema chronicum migrans of early Lyme disease, gout, septic arthritis, septic bursitis, vasculitis, allergic reaction to an insect bite, acute drug reaction, deep venous thrombosis and diffuse inflammatory carcinoma of the breast. Differentiating from cellulitis<unk>  can be distinguished from cellulitis by two particular features; its raised advancing edge and its sharp borders. The redness in cellulitis is not raised and its border is relatively indistinct. Bright redness of<unk>  has been described as a third differentiating feature.<unk>  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.
Erysipelas
Cellulitis
Staphyloma
Contact stomatitis
Demodicosis
Erysipeloid
Streptococcal intertrigo
Dermatitis repens