Chapter 117. Folliculitis

A 42-year-old woman is seen for multiple papules and pustules on her back (Figure 117-1). Further questioning demonstrates that she was in a friend's hot tub twice over the previous weekend. The outbreak on her back started after she went into the hot tub the second time. This is a case of Pseudomonas folliculitis or “hot tub” folliculitis. The patient avoided this hot tub and the folliculitis disappeared spontaneously. Another option is to treat with an oral fluoroquinolone that covers Pseudomonas.

Folliculitis is an inflammation of hair follicles usually from an infectious etiology. Multiple species of bacteria have been implicated, as well as fungal organisms.

• Folliculitis is a cutaneous disorder that affects all age groups and races, and both genders.
• It can be infectious or noninfectious. It is most commonly of bacterial origin (Figures 117-2 and 117-3).
• Pseudofolliculitis or sycosis barbae is most frequently seen in men of color and made worse by shaving (Figure 117-4).1
• Acne keloidalis nuchae or keloidal folliculitis is commonly seen in black patients, but can be seen in patients of any ethnic background (Figures 117-5 and 117-6).2
• Eosinophilic folliculitis is described in patients with HIV infection (Figure 117-7).
• Methicillin-resistant Staphylococcus aureus (MRSA) can pose a challenge to the treatment of folliculitis (Figure 117-8).

• Folliculitis is an infection of the hair follicle and can be superficial, in which it is confined to the upper hair follicle, or deep, in which inflammation spans the entire depth of the follicle.
• Infection can be of bacterial, viral, or fungal origin. S. aureus is by far the most common bacterial causative agent.
• The noninfectious form of folliculitis is often seen in adolescents and young adults who wear tight-fitting clothes. Folliculitis can also be caused by chemical irritants or physical injury.
• Topical steroid use, ointments, lotions, or makeup can swell the opening to the pilosebaceous unit and cause folliculitis.
• Bacterial folliculitis or Staphylococcus folliculitis typically presents as infected pustules most prominent on the face, buttocks, trunk, or extremities. It can progress to a deeper infection with the development of furuncles or boils (Figure 117-9). Infection can occur as a result of mechanical injury or via local spread from nearby infected wounds. An area of desquamation is frequently seen surrounding infected pustules in S. aureus folliculitis.1-3
• Parasitic folliculitis usually occurs as a result of mite infestation (Demodex). These are usually seen on the face, nose, and back and typically cause an eosinophilic pustular-like folliculitis.1
• Folliculitis decalvans is a chronic form of folliculitis involving the scalp, leading to hair loss or alopecia (Figure 117-10). Staphylococci infection is the usual causative agent, but there also has been a suggested genetic component to this condition.1 It is also called tufted folliculitis because some of the hair follicles will have many hairs growing from them simultaneously (Figure 117-11) (see Chapter 189, Scarring Alopecia).
• Acne keloidalis nuchae is a chronic form of folliculitis found on the posterior neck that can be extensive and lead to keloidal tissue and alopecia.1-3 Although it is often thought to occur almost exclusively in black men, it can be seen in men of all ethnic backgrounds and occasionally in women (Figures 117-5 and 117-6) (see Chapter 114, Pseudofolliculitis and Acne Keloidalis Nuchae).
• Fungal folliculitis is epidermal fungal infections that are seen frequently. Tinea capitis infections are a form of dermatophytic folliculitis (see Chapter 137, Tinea Capitis). Pityrosporum folliculitis is caused by yeast infection (Malassezia species) and is seen in a similar distribution as bacterial folliculitis on the back, chest, and shoulders (Figure 117-12) (see Chapter 141, Tinea Versicolor). Candidal infection is less common and is usually seen in individuals who are immunosuppressed, present in hairy areas that are moist, and unlike most cases of folliculitis, may present with systemic signs and symptoms.1-4
• Pseudomonas folliculitis or “hot tub” folliculitis is usually a self- limited infection that follows exposure to water or objects that are contaminated with Pseudomonas aeruginosa (Figure 117-1). This occurs when hot tubs are inadequately chlorinated or brominated. This also occurs when loofah sponges or other items used for bathing become a host for pseudomonal growth. Onset of symptoms is usually within 6 to 72 hours after exposure, with the complete resolution of symptoms in a couple of days, provided that the individual avoids further exposure.4
• Gram-negative folliculitis is an infection with Gram-negative bacteria that most typically occurs in individuals who have been on long-term antibiotic therapy, usually those taking oral antibiotics for acne. The most frequently encountered infective agents include Klebsiella, Escherichia coli, Enterobacter, and Proteus.5
• Pseudofolliculitis barbae (razor bumps) is most commonly seen in black males who shave. Papules develop when the sharp edge of the hair shaft reenters the skin (ingrown hairs), and is seen on the cheeks and neck as a result of curled ingrown hair.2 It can also occur in women with hirsutism who shave or pluck their hairs (Figure 117-4) (see Chapter 114, Pseudofolliculitis and Acne Keloidalis Nuchae).6
• Viral folliculitis seen is primarily caused by herpes simplex virus and molluscum contagiosum.4 Herpetic folliculitis is seen primarily in individuals with a history of herpes simplex infections type I or II. But most notably, it may be a sign of immunosuppression, as is the case with HIV infection.7 The expression of herpes folliculitis in HIV infection ranges from simple to necrotizing folliculitis and ulcerative lesions. Molluscum is a pox virus and molluscum contagiosum has been well-documented in similar patient populations (i.e., HIV and AIDS) and in children (see Chapters 129, Herpes Simplex and 130, Molluscum Contagiosum).7-9
• Actinic superficial folliculitis is a sterile form of folliculitis seen predominantly in warm climates or during hot or summer months. Pustules occur primarily on the neck, over the shoulders, upper trunk, and upper arms, usually within 6 to 36 hours after sun exposure.10
• Eosinophilic folliculitis is associated with HIV infection and can occur as a result of the viral infection itself, in which case the exact mechanism by which this occurs is uncertain (though thought to be auto­immune) (Figure 117-7).9,11,12,14 It is associated with diminished CD4 cell counts. Eosinophilic folliculitis generally improves with the initiation of highly active antiretroviral therapy (HAART), but can occur during the restoration of immune function with HAART.12

Often the diagnosis of folliculitis is based on a good history and physical.

Clinical Features

Folliculitis has its characteristic presentation as the development of papules or pustules that are thin-walled and surrounded by a margin of erythema or inflammation. Look for a hair at the center of the lesions (Figure 117-2). There is usually an absence of systemic signs and patients, symptoms range from mild discomfort and pruritus to severe pain with extensive involvement.

Typical Distribution

Any area of the skin may be affected and often location may be related to the pathogen or cause of folliculitis. The face, scalp, neck, trunk, axillae, extremities, and groin are some of the more common areas affected.

Laboratory Tests

Laboratory testing may be unnecessary in simple superficial folliculitis and where the history is clear and quick resolution occurs. Clinical diagnosis of herpes and fungal folliculitis may be difficult and diagnosis may be made based on strong clinical suspicion or as a result of failed antimicrobial therapy. KOH preps can be used to look for tinea versicolor or other fungal organisms. Herpes culture or a quick test for herpes can be used when herpes is suspected.1 SOR A

• Grover disease is a very pruritic condition of unknown cause that produces reddish papules and slight scale on the backs of middle-aged men. It is also called “transient acantholytic dermatosis” and may resolve spontaneously in a period of years. It resembles folliculitis but the papules are not centered on hair follicles (Figure 117-13).
• Miliaria is blockage of the sweat glands that can resemble the small papules of folliculitis. The eccrine sweat glands become blocked so that sweat leaks into the dermis and epidermis. Clinically, skin lesions may range from clear vesicles to pustules. These skin lesions primarily occur in times of increased heat and humidity, and are self-limited (see Chapter 108, Normal Skin Changes).1
• Impetigo is a bacterial infection of the skin that affects the superficial layers of the epidermis as opposed to hair follicles. It is contagious, unlike folliculitis. It has a bullous and nonbullous form, and honey-crusted lesions frequently predominate as opposed to the usual pustules seen in folliculitis (see Chapter 116, Impetigo).4,6
• Keratosis pilaris consists of papules that occur as a result of a buildup of keratin in the openings of hair follicles, especially on the lateral upper arms and thighs. It is not an infection but can develop into folliculitis if lesions become infected (see Chapter 145, Atopic Dermatitis).1,6
• Acne vulgaris is characterized by the presence of comedones, papules, pustules, and nodules that are a result of follicular hyperproliferation and plugging with excessive sebum. Inflammation occurs when Propionibacterium acnes and other inflammatory substances get extruded from the blocked pilosebaceous unit.15 Although acne on the face is rarely confused with folliculitis, acne on the trunk can resemble folliculitis. To distinguish between them look for facial involvement and comedones seen in acne (see Chapter 112, Acne Vulgaris).

• Management of folliculitis varies by causative agent and underlying pathophysiology.
• Antivirals, antibiotics, and antifungals are used as topical and/or systemic agents. Approaches to nonpharmacologic therapy include patient education on the prevention of chemical and mechanical skin irritation. Glycemic control in diabetic patients may help treat folliculitis.1-3 Good hygiene helps to control symptoms and prevent recurrence.
• With superficial bacterial folliculitis, treatment with topical preparations such as mupirocin (Bactroban) or fusidic acid may be sufficient.1 SOR A Additionally, topical clindamycin may be considered in the mildest cases in which MRSA is involved.1 SOR A
• Deep or extensive bacterial folliculitis warrants oral therapy with first-generation cephalosporins (cephalexin), penicillins (amoxicillin/clavulanate and dicloxacillin), macrolides, or fluoroquinolones.1,4,6 SOR A
• Pseudomonas or “hot tub” folliculitis usually resolves untreated within a week of onset (Figure 117-1). For severe cases, treatment with ciprofloxacin provides adequate antipseudomonal coverage.1,4 SOR B Application of a warm compress to affected areas also provides symptomatic relief.
• Pityrosporum folliculitis and/or tinea versicolor can be treated with systemic antifungals, topical azoles, and/or with shampoos containing azoles, selenium, or zinc (Figure 117-12) (see Chapter 141, Tinea Versicolor).
• Candidal folliculitis in immunosuppressed persons may be treated with oral itraconazole (see Chapter 136, Candidiasis).1 SOR A
• Demodex folliculitis can be treated with ivermectin or topically with 5% permethrin cream.4 SOR B
• Herpes folliculitis can be treated with acyclovir, valacyclovir, and famciclovir. Regimens may frequently include acyclovir 200 mg 5 times a day for 5 days (see Chapter 129, Herpes Simplex).1 SOR A
• Eosinophilic folliculitis associated with HIV is treated with HAART, topical steroids, antihistamines, itraconazole, metronidazole, oral retinoids, and UV light therapy.11 Topical steroids and NSAIDs and isotretinoin are treatments of choice for HIV-associated eosinophilic folliculitis.9-13 SOR B Relief with systemic antihistamines are variable and UV therapy is time-consuming and expensive.11,12 SOR C

Most cases of folliculitis are superficial and resolve easily with treatment. Dermatologic and surgical consultation may be required in cases of chronic folliculitis with scarring.

Prevention is most important, and centers on good personal hygiene and proper laundering of clothing. Patients should be encouraged to avoid tight-fitting clothing. Hot tubs should be properly cleaned and the chemicals should be maintained appropriately. Electric razors for shaving can help prevent pseudofolliculitis barbae and should be cleaned regularly with alcohol. Patients with acne keloidalis nuchae should avoid shaving the hair in the involved area.

Patient Resource

• http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001826/.

Provider Resource

• http://emedicine.medscape.com/article/1070456.