Etiology of PFB

In the 1950s, the the seminal studies by Kligman and Strauss [2] established that PFB lesions are indeed caused by ingrown hair which grow out of the follicle and then renter the skin. This propensity of hair to enter skin after exiting the follicle is the result of the curva­ture of the follicle structure. The curved follicle directs the hair exiting from follicle to come in very close contact with, or be embedded in the grooves of the skin at a short dis­tance from the follicle orifice. Their conclusions were based on skin biopsies from men with PFB, as well as direct visual observations and careful and exacting analysis using a surgical microscope. They reported that the only method for almost complete resolution of PFB was growing a beard, which allowed the hair to erupt from the skin after growing to depths of 2-3mm. It was proposed that the spring force of extended hair was insufficient to hold them in the skin as their length increased in a fashion similar to a coiled rope losing its tension as it length increases. They speculated that the skin texture of men with PFB prevents efficient shaving, as hair embedded in the grooves of skin were not accessible for full engagement of the cutting edge of blades and the uncut hair attained sufficient lengths to reenter the skin. Figure 18.1 is a skin biopsy of a subject with PFB, and demonstrates the propensity of curved hair to renter the skin after exiting the follicle. More recently, epilu – minescence dermatoscopy has dramatically reconfirmed the concordance between lesions and ingrown hair, and the demonstration of this hair – skin interaction to patients with PFB to enhance their compliance with treatments and improve treatment success by preventing hair from reentering the skin [6].

A study conducted at the Gillette research institute was designed to characterize the pat­tern of ingrown hair development in men with PFB. The number of actual ingrown hair in one-square-inch of facial skin in the neck region was quantified in six men with PFB using

a surgical microscope in order to quantify hair density and the percentage of ingrown hair. In six volunteers, the hair density ranged from 114 to 224 hair per square inch and the percent of ingrown hair ranged from 23 to 50% with an average of 33%. Not all ingrown hair were associated with lesions, but the substantial number of ingrown hair representing potential papule and pustule formation clearly demonstrates the difficulties and challenges in managing PFB. Indeed, it has been noted by dermatologists familiar with PFB that it is a very intractable and recalcitrant condition which can be managed, but not cured. In most men with PFB growing a beard can resolve the problem and informal estimates suggest a population of 10-20% of men who do not respond to growing a beard. To better understand the progression of PFB, we conducted a study on eight men whose PFB condition was resolved by abstaining from shaving for eight weeks. After resolving their PFB, the men began shaving every other day over a 15-day interval. We chronicled and quantified the recurrence of lesions during this period. In all subjects, the level of PFB in terms of total bump counts returned to pre – beard levels within 15 days of resumption of shaving. Figure 18.2 illustrates the dramatic and progressive return of lesions in one subject, whose response was typical of the group.

Poor shaving efficiency has traditionally been ascribed as the root cause of ingrown hair. A shaving study was designed to specifically characterize the quality of shaving efficiency in men with PFB. Images of hair in the circumscribed area of neck regions were captured with a video-microscope. The images were from circumscribed regions of the neck in 10 men with PFB, as well as 19 men not exhibiting PFB. Images were obtained before and after shaving to compare the efficiency of shaving in men with PFB versus men without PFB. Hair was characterized as fully cut at or below skin line, or only partially cut or totally missed after shaving. In men with PFB, only 41% of facial hair was fully cut at or below skin line, compared to over 81% in men without PFB. Men with PFB totally missed an average of 30% of hair compared to only 3% in men without PFB. This study clearly

confirmed the suggestions of earlier researchers that inefficient shaving was a causative factor promoting PFB. Design and development of more efficient means of mechanical hair removal remains a continuing challenge, as hair is often embedded in the grooves of the highly textured skin in men with PFB.