Folliculitis refers to inflammation of the hair follicle. It can be superficial or deep. In superficial folliculitis lesions are pustules with a central hair follicle and an erythematous base. In deep folliculitis, lesions are tender, firm, erythematous papules or nodules. In Part 1 we’ll focus on superficial folliculitis.
It’s important to pay close attention to the morphology of the lesions to determine if the pustules are follicular or non-follicular. Non-follicular pustules can be due to numerous dieases and often require a skin biopsy. See Table 2.
Bacterial folliculitis can occur in any body site. Triggering factors include sites with excess moisture, occlusion, post-shaving, waxing and topical steroid use. Patients with atopic dermatitis and diabetes may be at higher risk. Staph aureus is the commonest cause and a swab of a pustule can confirm the diagnosis. S. aureus carriage can be confirmed by bacterial culture of the nares, axilla and groin.
Treatment consists of avoiding predisposing conditions and antibiotic therapy, either topical or systemic, based on culture and sensitivity results. Cephalexin 500 mg by mouth 4x daily for 2 weeks can be used for most cases.
Culture negative (normal flora folliculitis) is characterized by pustules with normal flora on culture results. Acne, rosacea, and hidradinitis suppurativa may also show normal flora on culture. Treatment involves reducing overhydration and occlusion of skin. Anti-inflammatory antibiotics such as topical benzoyl peroxide, topical clindamycin, and oral tetracyclines can reduce the appearance of the lesions.
Gram negative folliculitis is due to proliferation of Gram negative organisms in the anterior nares with subsequent spread after long-term use of antibiotics. There may be multiple pustules with Enterobacter or Klebsiella or deep nodules with Proteus sp. Suspect this in patients with resistant pustules on the face and take a swab of a pustule for C & S. After the diagnosis is confirmed, a full course of oral isotretinoin is usually required.
Pseudomonas folliculitis presents as painful, follicular pustules, with significant inflammation, on the trunk and limbs after hot tub use. Gram stain and C & S can confirm the diagnosis with heavy growth of Pseudomonas aeruginosa. The treatment of choice is ciprofloxacin 500 mg po bid for 1 to 2 weeks.
Viral folliculitis is an unusual cause of folliculitis that’s more common in patients with recurrent facial herpes simplex virus infection who shave with a razor blade or in HIV+ patients. Viral culture and biopsy can help confirm the diagnosis. Valacyclovir 500 mg po tid for 5-10 days is often adequate.
Fungal folliculitis refers to folliculitis due to a dermatophyte infection, such as tinea barbae caused by T. mentagrophytes or T. verrucosum in farm workers and Majocchi’s granuloma caused by T. rubrum in women who shave their legs. Since the organism is deep within the hair follicle, topicals are rarely effective. Treatment is oral antifungal medication, such as terbinafine 250 mg po daily for 4 weeks.
Pityrosporum folliculitis typically occurs on the back and chest. Young adults are often affected especially with occlusion, excess sebum and warm weather. Other precipitating factors include antibiotic use and immunosuppression. Fungal microscopy reveals yeast forms. It’s treated similarly to pityriasis versicolour, with topical selenium sulfide shampoo and topical imidazoles (e.g. ketoconazole). Oral therapy is reserved for more extensive cases.
Demodex folliculitis may be associated with immunosuppression and typically occurs on the face and central chest. Scraping or biopsy can show numerous Demodex mites, which are part of the normal skin flora. Topical 5% permethrin cream can be helpful.
Drug-induced folliculitis should be suspected when there’s a monomorphous eruption of follicular pustules and papules on the trunk with an absence of comedones. Common causes include lithium, iodides, bromides, dilantin, steroids — anabolic and corticosteroids, isoniazid, and beta blockers. Discontinuing the drug can result in improvement. If this isn’t possible, then try anti-acne medications. The EGFR (epidermal growth factor receptor) inhibitors are being used more commonly in oncology and they typically produce an acneiform eruption. This eruption can be treated with topical steroids, emollients and oral doxycyline.
In disseminate and recurrent infundibulofolliculitis (DRIF) there are numerous skin-coloured follicular papules on the neck, chest, arms and buttocks that last years. Lesions look like “goose-bumps” and are typically in dark-skinned individuals. Treatment consists of keratolytic emollients and topical steroids. Oral isotretinoin for 4 months can be effective in resistant cases.
Look out for Part 2 on deep folliculitis next issue.
John Kraft, MD, FRCPC is a dermatologist in private practice in Markham and Thunder Bay, ON.
Charles Lynde, MD, FRCPC is an assistant professor of dermatology at the University of Toronto.
There are many causes of folliculitis, in addition to acne and rosacea.
Deep folliculitis (sycosis)