with or without a pustule on top ( Fig 66.2 ) Furunculosis is most commonly caused by SA and can be methicillin-sensitive or resistant (MRSA) Diagnosis is clinical but can be aided by ultrasound if it is unclear if there is fluctuance Therapy is with incision and drainage and adding antibiotic coverage is controversial The literature suggests antibiotics are not necessary for simple abscesses except in young children unless there is associated cellulitis, the lesion has failed incision and drainage previously, the patient is immunosuppressed or showing signs of sepsis, or the lesion is particularly difficult to drain Cultures can be sent from the purulent drainage in order to confirm the diagnosis and measure the antibiotic sensitivities Empiric therapy should be guided by local resistance patterns but is usually with clindamycin, trimethoprim-sulfamethoxazole, or doxycycline (if age appropriate) in order to cover for MRSA Recurrence of furunculosis is common Reinfection from the patient’s local environment can come from sources such as close contacts, pets, athletic equipment, or stuffed animals Reinfection may occur because of reinoculation from the patient’s own nares Decolonization is challenging but nasal decolonization may be effective with intranasal mupirocin two times daily for days for the patient and any close contacts Four percent chlorhexidine washes or dilute sodium hypochlorite (¼ cup in 20 to 40 gallons of water for 15 minutes) baths can be used to decolonize the skin