Differential diagnosis of folliculitis includes pseudofolliculitis barbae, eosinophilic folliculitis, keratosis pilaris, acne vulgaris, candidiasis, contact dermatitis, impetigo, and miliaria.13 Pseudofolliculitis barbae is an inflammatory reaction to shaving, more commonly seen in darkly pigmented skin. Pseudofolliculitis develops when the hair shaft penetrates the wall of the follicle or directly enters the epidermis.
Initial treatment for mild disease includes the elimination of predisposing factors such as occlusion, moisture, and abrasion. The area should be kept clean and dry, avoiding friction. For localized disease, prescribe topical clindamycin, mupirocin ointment, or benzoyl peroxide. If symptoms fail to respond, prescribe a 7-day course of antibiotic that targets methicillin-sensitive S aureus—eg, cephalexin or dicloxacillin. Also consider doxycycline, which has anti-inflammatory effects and is effective against MRSA. For refractory lesions, trimethoprim-sulfamethoxazole, clindamycin, or minocycline may be useful. If you suspect pseudomonas, consider giving ciprofloxacin for 10 to 14 days for persistent lesions or if the patient is immunocompromised.13,15 Consider obtaining bacterial, fungal, or viral cultures for lesions that fail to respond to initial treatment.
Furuncles/carbuncles/abscesses
A furuncle, commonly referred to as a boil, is an infected hair follicle that becomes enclosed, creating a collection of pus. A carbuncle is a collection of furuncles that converge and drain through a single opening. An abscess is a localized collection of pus arising from within the dermis that can extend within deeper tissues.5 Furuncles, carbuncles, and abscesses are managed similarly with drainage and consideration for MRSA risk factors.
S aureus is the most common cause of these infections; 59% of skin abscesses are due to community-acquired MRSA.16 Anaerobes may contribute to the polymicrobial flora of skin abscesses.17 Risk factors for MRSA infection include a history of previous MRSA infection, diabetes, dialysis or renal failure, placement of an indwelling catheter or medical device, injection drug use, incarceration, close contact with a person with known MRSA infection or colonization, long-term care residence, hospitalization or surgery within the past 12 months, and high prevalence of MRSA in the community.5
Ultrasound improves diagnostic accuracy. One study showed that when a clinical exam alone was inconclusive in evaluating skin and soft-tissue infections in children and adolescents, an ultrasound-assisted examination improved diagnostic accuracy.18 Sensitivity of the clinical examination was 43.7%, compared with 77.6% for the clinical examination plus ultrasound.18
Continue to: Incision and drainage first