Introduction to Folliculitis, furuncles, and carbuncles

Folliculitis: A bacterial infection of the hair follicle, folliculitis causes the formation of a pustule of the hair follicle opening. The infection can be superficial (follicular impetigo or Bockhart’s impetigo) or deep (sycosis barbae).

Furuncles, commonly known as boils, are another form of deep folliculitis. 

Carbuncles are a group of interconnected furuncles. 

The prognosis depends on the severity of the infection and the patient’s physical condition and ability to resist infection.

Causes
The most common cause of folliculitis, furuncles, or carbuncles is coagulasepositive Staphylococcus aureus. 

Predisposing factors include 

• an infected wound, 
• moisture, 
• obesity, 
• diabetes mellitus, 
• skin disease, 
• poor hygiene, 
• debilitation, 
• tight clothes, 
• friction, and 
• immunosuppressive therapy.

Signs and symptoms
Folliculitis, furuncles, and carbuncles have different signs and symptoms.

Folliculitis appears as a primary lesion in a small pustule located over a sebaceous orifice and may be perforated by a hair.

Furuncles are hard, painful nodules that commonly develop on the neck, face, breasts, perineum, thighs, axillae, and buttocks. For several days, these nodules enlarge and then rupture, discharging pus and necrotic material. After the nodules rupture, pain subsides, but erythema and edema may persist for days or weeks.

Carbuncles appear as multiple pustules or deep abscesses that drain through multiple openings onto the skin surface, usually around several hair follicles. Fever and malaise may accompany these lesions.

Diagnosis
The obvious skin lesion confirms folliculitis, furuncles, or carbuncles. Wound culture usually shows S. aureus. In carbuncles, patient history reveals preexistent furuncles. A complete blood count may show an elevated white blood cell count (leukocytosis).

Treatment

Appropriate treatment includes the following:

• Folliculitis is treated by cleaning the infected area thoroughly with antibacterial soap (such as Hibiclens) and water; applying warm, wet compresses to promote vasodilation and drainage from the lesions; applying topical antibiotics, such as mupirocin ointment, clindamycin or erythromycin solution; and, in extensive infection, administering systemic antibiotics (a cephalosporin or dicloxacillin) after culture and sensitivity results return.
• Furuncles may require incision and drainage of ripe lesions after application of warm, wet compresses and systemic antibiotics, as indicated by culture results, after drainage.
• Carbuncles require systemic antibiotic therapy as well as incision and drainage.