Non-purulent cellulitis usually has a rapid onset (less than one day). There may be associated lymphadenitis or erysipelas.
Risk factors in pediatrics for cellulitis are barrier disruption (including insect bites and chicken pox lesions) and chronic edema (e.g. spina bifida or congenital lymphedema). The most common cause is Streptococcus pyogenes (Group A streptococcus, GAS). Uncommonly, these may be due to S. aureus, especially if there is an open wound. MRSA seldom causes non-purulent cellulitis. Therefore in most typical cases, targeted anti-streptococcal therapy with penicillin provides optimal management (GAS is 100% susceptible to penicillin).
Early response to infection (within 24 hours) is evidenced as decreased pain and decreased intensity of erythema (not necessarily size), but initial worsening after antimicrobial initiation is not uncommon and does not represent treatment failure.
