Folliculitis has multiple causes. It is frequently caused by staphylococcal infection and may be more common in the diabetic patient. When the lesion is deep-seated, chronic, and recalcitrant on the head and neck, it is called sycosis.
Gram-negative folliculitis, which may develop during antibiotic treatment of acne, may present as a flare of acne pustules or nodules. Klebsiella, Enterobacter, Escherichia coli, and Proteus have been isolated from these lesions.
Hot tub folliculitis (Pseudomonas folliculitis), caused by Pseudomonas aeruginosa, is characterized by pruritic or tender follicular, pustular lesions occurring within 1–4 days after bathing in a contaminated hot tub, whirlpool, or swimming pool (eFigure 6–70). Flu-like symptoms may be present. Rarely, systemic infections may result. Neutropenic patients should avoid these exposures.
Hot tub folliculitis. (Used, with permission, from Lindy Fox, MD.)
Nonbacterial folliculitis may also be caused by friction and oils. Occlusion, perspiration, and chronic rubbing (eg, from tight jeans or other heavy fabrics on the buttocks and thighs) can worsen this type of folliculitis.
Steroid acne may be seen during topical or systemic corticosteroid therapy and presents as eruptive monomorphous papules and papulopustules on the face and trunk. It responds to topical benzoyl peroxide.
Eosinophilic folliculitis is a sterile folliculitis that presents with urticarial papules with prominent eosinophilic infiltration. It is most common in immunosuppressed patients, especially those with AIDS. It may appear first with institution of highly active antiretroviral therapy (ART) and be mistaken for a drug eruption.
Pseudofolliculitis is caused by ingrowing of tightly curled hairs in the beard area. In this entity, the papules and pustules are located at the side of and not in follicles. It may be treated by growing a beard, by using chemical depilatories, or by shaving with a foil-guard razor. Medically indicated laser hair removal is dramatically beneficial in patients with pseudofolliculitis and can be done on patients of any skin color.
Malassezia (Pityrosporum) folliculitis presents as 1- to 2-mm pruritic pink papulopustules on the upper trunk, hairline, and arms. It is often pruritic and tends to develop during periods of excessive sweating. It can also occur in immunosuppressed patients.
Demodex folliculitis is caused by the mite Demodex folliculorum. It presents as 1–2 mm papules and pustules on an erythematous base, often on the background of rosacea-like changes, in patients who have not responded to conventional treatment for rosacea. It is more common in immunosuppressed patients. KOH from the pustules will demonstrate Demodex folliculorum mites.
The symptoms range from slight burning and tenderness to intense itching. The lesions ...