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  • Author: Elizabeth K Satter, MD, MPH; Chief Editor: Dirk M Elston, MD  more...
Updated: Feb 09, 2016


Folliculitis is defined histologically as the presence of inflammatory cells within the wall and ostia of the hair follicle, creating a follicular-based pustule. The type of inflammatory cells varies depending on the etiology of the folliculitis and/or the stage at which the biopsy specimen was obtained.[1]

In superficial folliculitis, the inflammation is restricted to the infundibular aspect of the follicle, whereas in deep folliculitis the inflammation not only involves the deeper aspect of the follicle, it also extends into the surrounding dermis. Deep folliculitis can eventuate from chronic lesions of superficial folliculitis or from lesions that are manipulated, and may ultimately result in scarring.

Perifolliculitis, on the other hand, is defined as the presence of inflammatory cells, usually lymphocytes, within the perifollicular tissues with focal extension into the adjacent reticular dermis. Folliculitis and perifolliculitis can occur independently or together as a result of follicular disruption and irritation.

Acne represents a noninfectious form of folliculitis. Recently there has been a paradigm shift, and the pathogenesis of acne is now thought to be a primary inflammatory disorder since subclinical perifollicular inflammatory cells are seen even in early stages of acne, proceeding the development of the microcomedone. Hyperkeratinization then results in follicular obstruction, which allows for sebum accumulation resulting in further distension of the follicle. The normally commensal bacteria (Propionibacterium acnes) forms a biofilm and its lipases break down sebum triglycerides into proinflammatory fatty acids and activate the innate immune response through toll-like receptor-2.[2]

Acne-related Medscape articles include Acne Conglobata, Acne Fulminans, Acne Keloidalis Nuchae, Acne Vulgaris, and Acneiform Eruptions.



Folliculitis refers to inflammation of the hair follicle. It can be caused by an infection (bacterial, viral, fungal, or parasitic) or have a noninfectious etiology, most commonly as the result of follicular trauma, inflammation, or occlusion.

Eosinophilic folliculitis has a different etiology and is thought to occur as a result of an autoimmune process directed against the sebocytes or some component of the sebum.

Although the pathophysiology of the acneiform eruption secondary to epidermal growth factor receptor inhibitors is poorly understood, it is hypothesized that the papulopustular eruption occurs secondary to inhibition of follicular epidermal differentiation, which eventuates in follicular obstruction and subsequent inflammation.[3, 4, 5, 6]




Superficial folliculitis is common, but because it is often self-limited and patients rarely present to the doctor; therefore, the exact incidence is unknown. Those who are seen, more often have either recurrent or persistent superficial folliculitis or deep folliculitis. Although the incidence is unknown, conditions that make patients more susceptible include frequent shaving, immunosuppression, preexisting dermatoses, long-term antibiotic use, occlusive clothing and/or occlusive dressings, exposure to hot humid temperatures, diabetes mellitus, obesity, and use of EGF-R inhibitor medications.

Folliculitis has also been reported following smallpox or anthrax vaccine. These cases are more common in military troops who are vaccinated prior to being deployed.[7]

The acneiform eruption attributed to epidermal growth factor receptor inhibitors occurs in 50-100% of patients and is a dose-dependent drug reaction.[6]


Folliculitis occurs in persons of any race, but pseudofolliculitis and traction folliculitis occurs more commonly in African Americans, whereas classic eosinophilic folliculitis is more common in Japanese persons.[8, 9]


Although most cases of folliculitis show no sex predilection, eosinophilic folliculitis occurs more frequently in males and Pityrosporum folliculitis is seen slightly more often in females.


Folliculitis can be seen in persons of all ages.

Contributor Information and Disclosures

Elizabeth K Satter, MD, MPH Dermatologist and Dermatopathologist

Elizabeth K Satter, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American Medical Womens Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Paul Krusinski, MD Director of Dermatology, Fletcher Allen Health Care; Professor, Department of Internal Medicine, University of Vermont College of Medicine

Paul Krusinski, MD is a member of the following medical societies: American Academy of Dermatology, American College of Physicians, Society for Investigative Dermatology

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

Andrea Leigh Zaenglein, MD Professor of Dermatology and Pediatrics, Department of Dermatology, Hershey Medical Center, Pennsylvania State University College of Medicine

Andrea Leigh Zaenglein, MD is a member of the following medical societies: American Academy of Dermatology, Society for Pediatric Dermatology

Disclosure: Received consulting fee from Galderma for consulting; Received consulting fee from Valeant for consulting; Received consulting fee from Promius for consulting; Received consulting fee from Anacor for consulting; Received grant/research funds from Stiefel for investigator; Received grant/research funds from Astellas for investigator; Received grant/research funds from Ranbaxy for other; Received consulting fee from Ranbaxy for consulting.

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A 22-month-old boy with a staphylococcal folliculitis on the buttocks. The lesions have been excoriated. Diaper occlusion may have been related to onset of the rash.
A 30-year-old woman with hot tub folliculitis. She had used a hot tub 2 days prior, wearing a bikini-style bathing suit.
Pseudomonas folliculitis. Courtesy of Hon Pak, MD.
Superficial folliculitis with neutrophils concentrated in the upper aspect of the follicle
Perifolliculitis, showing inflammatory cells surrounding the follicle,
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