A plausible hypothesis for the clinical pattern of frontal fibrosing alopecia: The persistence of residues of leave‐on facial products on hairline and eyebrows

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Frontal fibrosing alopecia (FFA) is the most common cicatricial alopecia, and its incidence is exponentially growing. Although genetic predisposition and a hormonal imbalance are frequently implicated in its pathogenesis, the increasing incidence over the past years has raised questions about the role of environmental factors such as facial skincare products.1 This study aims to evaluate the distribution over time of leave-on products applied on the face, in order to identify a potential link between their residues left on skin and the pattern of hair loss observed in FFA. We compounded an oil-in-water emulsion with fluorescein 1:10 and applied it onto the face of eight healthy volunteers (1:1 female-to-male ratio), leaving it on for 24 h. During that day, volunteers were instructed to continue with their regular activities, including physical activity and gentle face cleansing. Several photographs of the volunteers through a wood lamp were taken at baseline and 8 and 24 h later to analyze the facial areas where the formula with fluorescein predominantly settled. A homogeneous yellow-reddish fluorescence was observed immediately after the application of the formula. In the pictures 8 h later, the fluorescent cream was progressively showing a preference for the frontotemporal hairline and eyebrows, as well as for the beard in male volunteers (specially the mustache area). The persistence of the formula residues in these areas becomes evident in the pictures 24 h after their initial application (Figures 1 and 2). A recent systematic review and meta-analysis revealed an elevated risk of FFA with a 3.02-fold higher likelihood associated with sunscreen use and a 2.20-fold higher likelihood with moisturizers.2 Interestingly, despite women have historically incorporated facial skincare products into their daily routine, the surge of FFA over the past 15–20 years coincides with the trend of including ultraviolet filters among the components of most cosmetic products.3 Proposed mechanisms for sunscreen involvement in FFA pathogenesis include immune lichenoid reactions, oxidative stress induced by titanium dioxide nanoparticles in physical sunscreens, systemic absorption of chemical filters potentially causing endocrine disruption and, finally, the blockage of the immunomodulatory effects of sunlight.1, 4 The predilection of FFA for postmenopausal women may be partially attributed to a reduced sebum production, resulting in the accumulation of pathogenic components in the follicular infundibulum.3 However, it is essential to note that while numerous case–control studies have demonstrated a statistical association between leave-on facial products and FFA, they remain susceptible to recall2 and selection bias.4 Our study provides an experimental model that supports the involvement of external topical agents in the etiopathogenesis of FFA. Even though individuals maintained their regular lifestyle and face-washing routines, residues of the leave-on facial products persisted predominantly in FFA-typically affected areas even after 24 h. The implication of topical agents is also supported by the observation of a female patient who developed FFA exactly in the same areas where she had been applying her sunscreen daily for many years, including the frontal hairline and mid-scalp.5 Furthermore, Cranwell and Sinclair even reported the case of a patient with FFA who exhibited hair regrowth in the frontal hairline after ceasing sunscreen use.6 In conclusion, when applied on the face, our compounded cream remained predominantly in the frontotemporal hairline and eyebrows and, in the case of males, in the beard area as well. This distribution aligns with the clinical pattern of hair loss observed in FFA. Although the role of facial leave-on products such as sunscreens in the etiopathogenesis of FFA is still controversial, we believe that our observation may provide a plausible hypothesis to explain the clinical pattern in FFA. All authors have contributed and reviewed the final version of this manuscript. A written consent form was obtained from volunteers who have participated in this study. Not Applicable.

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