Hairs involved over the chin and neck are usually curled. Shaving or plucking cuts hairs on an angle. The hairs then curl inward retracting into the follicle where they incite a foreign body reaction. This results in acne formation (e.g., papules and pustules), with fibrosis of the follicle, scarring alopecia, and eventually keloidal scar formation in some susceptible males [4]. Magnification will reveal a trapped hair in the follicle in early lesions prior to inflammatory response to the trapped hair.

Some therapies and illnesses are known to affect the appearance of PFB. Medications promoting hirsutism including cyclosporine [5] and oral minoxidil [6] can initiate PFB formation. Renal transplant patients may note hyperplastic PFB lesions [7]. Scar sarcoidosis can occur in PFB lesions [5]. Pathogenesis may relate in part to mutation in hair follicle-specific keratin, the K6hf polymorphism [8, 9].

Topical therapy includes steaming the cheek before shaving, freeing trapped hairs with a tweezer, and application of benzoyl peroxide-based shaving cream to the face prior to shaving. Shaving should be performed using a specialized razor with a grid over the blades to reduce aggressively close shave, stroking the beard with the blade in the direction of the grain of the hair and following shaving with acne therapies, e.g., topical clindamycin/topical benzoyl peroxide combination agent [10], topical retinoids, and/or topical antibiotic agents [11, 12]. Emollients and exfoliants to open the follicle can aid in avoidance of skin lesions. When conservative measures fail, hair removal laser with long-pulsed diode, alexandrite, or long-pulsed Nd:Yag lasers can be used to reduce hair thickness and growth in the inflamed follicles as well as to reduce dyspigmentation, papule formation, and cobblestoned appearance. Long-pulsed lasers are used to reduce risk of absorption by cutaneous melanin and consequent depigmentation. Dosages should be conservative to avoid induction of dyspigmentation in the darkest patients [13–16]. Photodynamic therapy has also been described for lesion reduction [17]. Eflornithine can be used to reduce hair size and enhance results from laser [18]. Hydroquinones and other lightening agents with adjunctive sun protection can be used for post-inflammatory pigmentary alteration. Intralesional corticosteroids in dilute concentrations can be used to reduce the size of hypertrophic scars and keloidal lesions [19, 20]. In the event of lack of response, shaving can be stopped altogether and can be replaced by depilatories [21, 22]. Isotretinoin has been described as being mildly successful at lesional clearance temporarily as well [23].

Although few older men are noted to have PFB, disease can be active from adolescence through senescence. In women, a thorough medical history for hair-inducing drugs or hormonal abnormalities (e.g., irregular menses, deep voice) is needed and diagnosis may merit laboratory evaluation and/or endocrinological referral.