A Knot in the Truth
In this endeavor to untangle the truth, it should be remembered that at the time of writing, the purported association between FFA and ACD remains debatable. Contact dermatitis specialists have voiced that the association between FFA and ACD, especially with regard to sunscreen, cannot be supported due to the lack of sufficient evidence.29 A large majority of the research conducted on FFA and ACD is based on case reports and studies limited to a small sample size, and most of these patch test studies lack a control group. Felmingham et al30 noted that the recent epidemiology of FFA aligns with increased sunscreen use. They also highlighted the limitations of the aforementioned studies, which include misclassification of exposures in the control group2 and recall bias in questionnaire participants.2,12 The most pressing limitation that permeates through most of these studies is the temporal ambiguity associated with sunscreen use. A study by Dhana et al31 failed to specify whether increased sunscreen use preceded the diagnosis of FFA or if it stems from the need to protect more exposed skin as a consequence of disease. Broad sunscreen avoidance due to concern for a possible association with hair loss could have detrimental health implications by increasing the risk for photodamage and skin cancer.
FFA Patch Testing
The avoidance of pertinent allergens could be effective in reducing local inflammation, pruritus, and erythema in FFA.9,14,32 At our institution, we selectively patch test patients with FFA when there is a suspected contact allergy. Clinical features that may allude to a potential contact allergy include an erythematous or eczematous dermatitis or symptoms of pruritus along the scalp or eyebrows. If patients recall hair loss or symptoms after using a hair or facial product, then a potential contact allergy to these products could be considered. Patch testing in patients with FFA includes the North American 80 Comprehensive Series and the cosmetic and hairdresser supplemental series, as well as an additional customized panel of 8 allergens as determined by patch testing experts at the University of Massachusetts, Brigham and Women’s Hospital, and Massachusetts General Hospital (private email communication, November 2017). Patch test readings are performed at 48 and 96 or 120 hours. Using the American Contact Dermatitis Society’s Contact Allergen Management Program, patients are provided personalized safe product lists and avoidance strategies are discussed.
Final Interpretation
In a world where cosmetic products are ubiquitous, it is hard to define the potential role of contact allergens in the entangled pathogenesis of FFA and ACD. As evidenced by emerging literature that correlates the 2 conditions and their exacerbating factors, it is important for physicians to have a comprehensive diagnostic approach and heightened awareness for potential allergens at play in FFA (Table). The identification of certain chemicals and preservatives as potential triggers for FFA should emphasize the importance of patch testing in these patients; however, whether the positive reactions are relevant to the pathogenesis or disease course of FFA still is unknown. While these findings begin to unravel the intertwined causes of FFA and ACD, further research encompassing larger cohorts and prospective studies is imperative to solidify these associations, define concrete guidelines, and improve patient outcomes.
