furuncles

A furuncle, also known as a boil, is a deep skin infection of a hair follicle and surrounding tissue caused most often by Staphylococcus aureus. It begins as a tender, red nodule that may become filled with pus and develop a central fluctuant area. When several furuncles arise from adjacent follicles and merge into a larger abscess, the condition is called a carbuncle.

Furuncles result from bacterial invasion of the hair follicle or nearby sebaceous units and are facilitated by factors such as minor skin trauma, friction, poor hygiene, diabetes, immunosuppression, or humid environments. Staphylococcus aureus is the usual pathogen, with methicillin-resistant strains increasingly encountered in communities and healthcare settings. Most infections are localized to the skin, but spreading infection or bacteremia can occur in rare cases.

Clinically, furuncles present as a painful, swollen, erythematous nodule that enlarges over days and may drain spontaneously or require incision and drainage if fluctuant. Surrounding cellulitis may be present. Diagnosis is usually clinical; pus or exudate can be cultured if needed, especially in persistent or recurrent cases or to guide antibiotic therapy. Ultrasound can help distinguish an abscess from inflammatory tissue in uncertain cases.

Treatment emphasizes local care and selective antibiotic use. Warm compresses promote drainage. Incision and drainage by a clinician is often sufficient for a fluctuating lesion. Antibiotics are added for extensive surrounding cellulitis, fever, rapid spreading, facial lesions, diabetes, immunosuppression, or multiple lesions. When antibiotics are prescribed, options typically cover Staphylococcus aureus, with coverage for MRSA in appropriate settings. Good hygiene and wound care help prevent recurrence.