Cellulitis
Cellulitis is a bacterial skin infection, managed per the IDSA 2014 Practice Guidelines for Skin and Soft Tissue Infections.
Symptoms
Warm, red, swollen, tender skin, usually on a leg, that spreads over days; fever and chills can accompany more significant infections.
Causes and risk
Streptococcus and Staphylococcus species (including MRSA in some cases) are the usual culprits, entering through a skin break, insect bite, or area of chronic swelling. MRSA coverage is added specifically for purulent drainage, penetrating trauma, known MRSA history, injection drug use, or signs of systemic illness.
How it is evaluated
Diagnosis is clinical. Imaging or labs are reserved for uncertain diagnosis or signs of a deeper or more severe infection.
Treatment
Streptococcal-active oral antibiotics (penicillin, amoxicillin, dicloxacillin, cephalexin, or clindamycin) are first-line for a standard 5-day course, extended if not improving, per IDSA guidance.
When to seek care
Pain out of proportion to how the skin looks, rapid spread, purple or blood-filled blisters, or a crackling sensation under the skin can signal necrotizing infection, a surgical emergency -- normal-looking skin and vital signs do not rule it out, so any of these findings need immediate emergency evaluation.