Furuncle

A furuncle, also known as a boil, is an infected hair follicle with extension through the dermis into the subcutaneous soft tissues (cf. folliculitis, a more superficial hair follicle infection, with pus limited to the epidermis).

Epidemiology

Risk factors

Outbreaks of furunculosis are seen, with known risk factors:

• closely cohabiting individuals, e.g. the incarcerated, families
• contact sports
• poor personal hygiene
• close contact to those with furuncles
• infected fomites

Clinical presentation

Most patients complain of a painful reddened nodular skin lesion with a discharge. Commonly they arise in the axillae or buttocks, due to the extensive hair follicles in these regions. They may be multiple³.

Pathology

Most furuncles are due to Staphylococcus aureus infection. A furuncle comprises a focal inflammatory nodule with a hair follicle passing through it, with a small hypodermal abscess ^1,3.

Treatment and prognosis

Small furuncles often resolve with damp heat application only. Larger furuncles, and all caruncles, require incision and drainage.In general, systemic antimicrobial chemotherapy is unnecessary unless there are complications such as cellulitis ¹.

Furuncles may also form outbreaks, necessitating community-wide measures, e.g. thorough laundering of bedclothes, towels and clothing, avoiding crowded environments, non-sharing of towels and flannels, and a fastidious approach to personal hygiene; occasionally the systematic treatment of S. aureus found colonising individuals may also be needed ¹.

Complications

• recurrent furunculosis may occur in some individuals, and other than a few immunocompromised patients, in particular children, most patients have skin carriage of S. aureus as their only risk factor ¹

A furuncle which is suboptimally managed may progress to ¹:

• carbuncle (a cluster of furuncles)
• cellulitis
• skin abscess
• sepsis .