▶Definitions
■Folliculitis: superficial inflammation centered around a follicle
■Furuncle: bacterial folliculitis of a single follicle that involves a deeper portion of the follicle
■Carbuncle: bacterial folliculitis that involves the deeper portions of several contiguous follicles
▶Types of folliculitis include
■Bacterial folliculitis (the most common type) is most often caused by Staphylococcus aureus. While many of these isolates are still methicillin-sensitive S aureus (MSSA), some may be methicillin-resistant S aureus (MRSA).
■Pseudomonas (hot tub) folliculitis is usually caused by gram-negative bacteria (most often Pseudomonas aeruginosa).
■Gram-negative bacteria can also cause folliculitis in acne patients receiving long-term antibiotic therapy.
■Malassezia (Pityrosporum), a yeast, may be a cause of folliculitis localized to the back, upper chest, shoulders, and upper arms.
■Demodex (a skin mite) folliculitis presents as an erythematous follicular papulopustular eruption on the face, usually in immunocompromised hosts (eg, children receiving chemotherapy for leukemia).
▶Predisposing conditions for furuncles and carbuncles include obesity, diabetes, and immunodeficiency, as well as warm, humid climates.
▶Folliculitis is characterized by discrete follicular-centered pustules with surrounding erythema (Figures 26.1 and 26.2).
■The most common locations are the buttocks and thighs, especially in young children.
■Occasionally, folliculitis can be seen in areas that are subject to occlusion and irritation from clothing.
■Lesions are most often painless; however, they can be mildly tender and may be pruritic.
■Pseudomonas folliculitis often presents with localization of lesions to areas covered by the bathing garment.
▶Furuncles/carbuncles present as erythematous papulonodules or nodules, often with a central punctum (Figure 26.3).
■The central area tends to be the point where fluctuance will develop.
■Pain is common, and fever may be present.
■Pain diminishes following drainage of the lesion.
▶Skin and soft tissue infections due to community-acquired MRSA often present as furuncles and carbuncles.
■Lesions typically are erythematous, fluctuant, and painful.
■They may reveal purulent drainage.
■Other family or household members may have (or previously have had) similar lesions.
Look-alikes
Disorder | Differentiating Features |
Folliculitis from opportunistic organisms (especially in immunocompromised patients) | •Persistent despite appropriate therapy. •Patients with leukopenia may show less erythema than expected. |
•Erythematous papules and macules. •Pustules usually lacking. •Lesions not centered around hair follicles. •Other symptoms (eg, upper respiratory, gastrointestinal) may be present. | |
Insect bites | •Usually have a central punctum present on close inspection. •Most often occur on exposed areas. •Extreme pruritus common. •May see linear groupings (“breakfast, lunch, and dinner” sign), especially with flea bites. •Pustules rare. •Lesions not centered around hair follicles. |
Acne nodule | •May look very similar to a carbuncle, but typical acne lesions (eg, open and closed comedones) usually also present. •Lesions typically are limited to face, chest, shoulders, and back. |
•Recurrent papules, cysts, sinus tracts, and nodules that heal with scarring. •Typically located in axillary and inguinal regions; occasionally involve posterior auricular area. |
▶The diagnosis is usually made clinically.
▶Skin swab for bacterial culture will usually reveal the causative agent.
▶When furuncles or carbuncles are drained, a swab of the contents should be sent for bacterial culture and sensitivities.
▶Preventive measures include
■Avoid tight-fitting clothing.
■Lose weight (if applicable).
■Use antibacterial cleansers such as those that contain chlorhexidine (avoid ear canals) or sodium hypochlorite.
■For nasal carriers of S aureus, intranasal mupirocin (for patient and family contacts) may diminish recurrences.
■Patients who are prone to frequent recurrences may benefit from bleach baths: ¼ to ½ cup of sodium hypochlorite solution (liquid bleach) added to a full bathtub of water and used as a soak for 10 minutes twice weekly. Use of a sodium hypochlorite cleanser (as noted previously) is another option.
▶Treatment for folliculitis
■Antibacterial skin cleansers, including chlorhexidine (avoid ears), or sodium hypochlorite.
■Topical antibiotic may suffice for mild cases (eg, clindamycin, mupirocin, retapamulin).
■Oral antistaphylococcal antibiotic (eg, cephalexin, dicloxacillin) for 7 to 10 days for severe cases. If MRSA is suspected or isolated, use of clindamycin, doxycycline (in children >8 years), trimethoprim-sulfamethoxazole, or another appropriate agent (as determined by antibiotic sensitivity testing) is indicated.
■Culture of purulent material whenever possible.
▶Treatment for furunculosis and carbunculosis
■Warm, moist compresses to promote or facilitate drainage.
■Incision and drainage may be necessary for larger or more fluctuant lesions or if the process is caused by MRSA. Incision and drainage is recommended as initial therapy for MRSA-associated furuncles and carbuncles, with or without antibiotics.
■Skin swab of pustular fluid should be sent for bacterial culture.
■Oral antistaphylococcal antibiotic (eg, cephalexin, dicloxacillin) for 7 to 10 days for MSSA; if MRSA is suspected or isolated, use of clindamycin, doxycycline (in children >8 years), trimethoprim-sulfamethoxazole, or another appropriate agent (as determined by antibiotic sensitivity testing) is indicated.
■Intermittent short courses of rifampin are recommended by some for patients with frequent or moderate to severe recurrences.
▶In children with typical immunity the prognosis is excellent.
▶Recurrence is common, especially in the continued presence of common risk factors.
▶Immunocompromised individuals may have infections with unusual organisms that are more difficult to diagnose and treat.
▶Consider referral to a dermatologist for patients who have severe or extensive disease or do not respond to standard treatments. If the patient develops a severe infection with MRSA that requires hospitalization, an infectious disease specialist should be consulted.
▶Centers for Disease Control and Prevention: Patient information on Pseudomonas (hot tub) folliculitis (in English and Spanish).
https://www.cdc.gov/healthywater/swimming/swimmers/rwi/rashes.html
▶Centers for Disease Control and Prevention (in English and Spanish): MRSA in health care settings. Has patient information materials.
▶MedlinePlus: Information for patients and families (in English and Spanish) sponsored by the US National Library of Medicine and National Institutes of Health.