Facial Hair Phenotypes and Regional Differences

Female facial hair can present itself as a coarse terminal hair in a male-type pattern in the upper lip and chin regions (hirsutism), or as a finer vellus-type on the chin and cheeks. The characteristics of vellus-type hair in terms of its density and pigmentation are more com­monly associated with genetic extraction but, nonetheless, are largely unwanted. It has been suggested that the size of the dermal papilla compartment is correlated with the size (diameter) of the hair follicle [21]. More recently, Elliot et al. [15] reported that the dermal papilla volume from hair follicles derived from terminal male facial hair follicles was nearly 40 times greater than that of female facial vellus follicles. Moreover, the increase in dermal papilla volume was associated with a 17-fold increase in the number of cells and a 2.4-fold increase in the volume of each cell. These data suggest that the transition of a follicle from vellus to terminal hair phenotype or vice versa is, at least in part, related to the number of cells and/or the average extracellular matrix volume in the dermal papilla compartment.

The majority of clinical evaluations and products research to date has been focused upon identifying technologies that impact terminal hairs. This hair is pigmented to varying shades and is what consumers shave or manage via other means on a daily to weekly basis. Among females, body sites may include underarms, lower legs, bikini areas, as well as upper lip and chin. In contrast, vellus hair is present on all parts of the body with the excep­tion of plantar skin and is somewhat less noticeable, since it is generally nonpigmented, and does not grow as aggressively, nor as long as terminal hair. It is typically referred to as “peach fuzz” and Western consumers are fearful of the myth that if they shave this hair, it will transform into a pigmented terminal hair and will worsen the condition.

It has been suggested that an average of 10% of vellus hair follicles are actively growing (anagen) and 90% are in the resting phase (telogen). However, it has been reported [22] that female cheek vellus hairs are in a 44:56 ratio of anagen to telogen, in contrast to 90:10 ratio. The ratio of 44:56 is similar to what has been determined for female forearm hairs, which are very fine terminal hairs with relatively low pigmentation content (P&G unpub­lished data).

Published technical literature on vellus hair is very limited. There have been some histo­logical evaluations of vellus hair follicles that found unique attachments of the erector pili muscle to the outer root sheath of the hair, particularly in facial vellus hairs. This difference is morphologically ascribed as a “skirt” structure that is different than that present in termi­nal hair. In addition, there is a high concentration of CD34+ cells localized around the “skirt”, suggesting the presence of bulge cells as found in terminal hair. The physiological role of the skirt, however, remains unclear.

In an attempt to characterize facial vellus hair, we analyzed via scanning through an electron microscope, the hair diameter and cuticle patterning of individual facial vellus hair collected from the middle jawline areas of nine panelists (10 hair per panelist). Two of the nine panelists had jawline hairs that were pigmented. While these hair were more similar to terminal hair in appearance, their overall length on the face suggests vellus like growth properties. Figure 6.3 highlights the hair diameter values calculated and the graph shows diameter values from all nine panelists, including the two with pigmented jawline hairs. The hair diameter ranged from about 12 pm to just over 30 pm with an average of 22 pm for all hair. Although the panel size was small, these preliminary findings suggest that vel – lus hair diameters are significantly smaller than the typical diameter of terminal hairs pres­ent on scalp and body (50-150 pm).

Scanning electron microscopy (SEM) was used to visualize hair fibers from vellus and terminal hair. The SEM images below compare Type I and Type II upper lip hairs to facial vellus and scalp terminal hairs. Type I hair resemble terminal scalp hair, not only in diam­eter but also in cuticle pattern, whereas Type II hairs appear more like vellus hair regarding these parameters (Fig. 6.4). These insights may serve as a basis for the identification of different technologies or regimens toward the removal of unwanted facial hair.

To assess the efficacy of chronic technologies on vellus hair, a study was conducted at Bower Research Center (Boulder, CO) in 65 women (40 placebos; 25 Vaniqa) with upper lip hair. The effect of Vaniqa™ on Type I and Type II facial hair was evaluated following twice daily application for 12 weeks. Half-face digital images and Hi-Scope images (Fig. 6.5) were captured at baseline, 4, 8, and 12 weeks. The study also included self­assessments and focus groups. Vaniqa™ elicited a 51% (significant at p < 0.05) reduction of average growth rate in Type I hair at week 4, which was maintained through weeks 8 and 12 (Fig. 6.6). With Type II facial hair, Vaniqa elicited as much as a 35% reduction in aver­age growth rate at week 4, with a significant reduction at weeks 8 and 12 (Fig. 6.7).

Earlier analysis of human facial vellus hair showed that the average diameters were sig­nificantly less than human terminal hair. While terminal hairs range from 40 to 150 цт, vellus hairs were typically 20-27 ^m in diameter, with the higher diameters being from pigmented vellus hair. It was noted that the spacing of the cuticle plates on the outside of the hair was larger on vellus hair when compared to terminal hair. To address this issue, we provided STEM visualization of vellus hairs and compared them with images of terminal hair. The number of cuticle layers ranged from 2 to 5 for vellus hairs, whereas for terminal hairs it ranged from 5 to 12 (Fig. 6.8) and the diameter measurements as noted earlier were

Figure 6.6 Effect of Vaniqa™ on Type I facial hair based on Hi-Scope image analysis.

confirmed. Thus, female facial vellus hair can be viewed as having an overall geometrical and structural differential that is approximately half of that seen with coarser terminal hairs. It was hypothesized that the seemingly weaker nature of vellus hairs could render them susceptible to a depilatory formula with lower thioglycolate levels and pH ranges. This could translate to an effective depilatory that may have a lower irritation profile. This

Week 8

Figure 6.8 STEM of a partial cross section from a vellus hair and terminal hair with arrows depicting the cuticle layers.

may also hold true for pigmented vellus hair since the diameters are still significantly less than those of terminal hair.

While not a common occurrence, vellus and terminal hair are able to transition from one state to another based on dramatic changes as hormonal alterations, severe dietary alterations, laser therapy, or as a drug-induced side effect. Historically, it has been viewed that vellus hair on the body exists as a fairly dormant follicular unit. The cycle has been described as very slow with only 10% of hair being in an active growing state at any given time, with the remaining being in the telogen resting phase. In addition, it was thought that the hair represents a slower growth population and is not androgen-dependent like terminal hairs. However, efforts by Blume et al. [22] more closely examined these population distributions between vellus and terminal hairs and differences between male and females. Several key observations include:

• Greatest density of vellus hair was on forehead and cheeks, followed by back, shoulder, and chest

• Forty-six to forty-nine percent of vellus hair on cheeks and forehead were growing

• Vellus hair showed a 4-10-fold slower growth rate than terminal hair.

• Overall hair growth was not affected by sex or age, even though the maximum length of vellus hair decreased as a function of aging.

• No correlation between sebum excretion rates and vellus hair growth was found.

In summary, the findings from this study set the stage for establishing a model for both identifying key technical drivers for consumer noticeability of unwanted facial hair, and establishing the success criteria for identifying acute and chronic intervention technolo­gies. This will allow for calculation of what percentage inhibition of hair growth must occur from a topical in order to significantly shift the timing for appearance of vellus hair that signals a “need to manage” point.