Does sunscreen cause frontal fibrosing alopecia?
Dermatologists are confronting the conundrum of rising cases of frontal fibrosing alopecia (FFA). Several theories on the pathogenesis of this idiopathic scarring alopecia have been raised, one of which involves increased use of sunscreen. Proposed explanations for sunscreen’s role in FFA include a lichenoid reaction inducing hair follicle autoimmunity through an unclear mechanism; a T cell–mediated allergic reaction, which is unlikely according to contact dermatitis experts14; reactive oxygen species production by titanium nanoparticles, yet titanium has been detected in hair follicles of both patients with FFA and controls15; and endocrine disruption following systemic absorption, which has not been supported by any high-quality human studies.7
An association between facial sunscreen use and FFA has been reported in case-control studies16; however, they have been criticized due to methodologic issues and biases, and they provide no evidence of causality.17,18 The jury remains out on the controversial association between sunscreen and FFA, with a need for more convincing data.
Does sunscreen impact coral reef health?
Coral reefs—crucial sources of aquatic biodiversity—are under attack from several different directions including climate change and pollution. As much as 14,000 tons of sunscreen enter coral reefs each year, and chemical sunscreen filters are detectable in waterways throughout the world—even in the Arctic.19,20 Thus, sunscreen has come under scrutiny as a potential environmental threat, particularly with coral bleaching.
Bleaching is a process in which corals exposed to an environmental stressor expel their symbiotic photosynthetic algae and turn white; if conditions fail to improve, the corals are vulnerable to death. In a highly cited 2016 study, coral larvae exposed to oxybenzone in artificial laboratory conditions displayed concentration-dependent mortality and decreased chlorophyll fluorescence, which suggested bleaching.19 These findings influenced legislation in Hawaii and other localities banning sunscreens containing oxybenzone. Problematically, the study has been criticized for acutely exposing the most susceptible coral life-forms to unrealistic oxybenzone concentrations; more broadly, there is no standardized approach to coral toxicity testing.21
The bigger picture (and elephant in the room) is that the primary cause of coral bleaching is undoubtedly climate change/ocean warming.7 More recent studies suggest that oxybenzone probably adds insult to injury for corals already debilitated by ocean warming.22,23
It has been posited that a narrow focus on sunscreens detracts attention from the climate issue.24 Individuals can take a number of actions to reduce their carbon footprint in an effort to preserve our environment, specifically coral reefs.25 Concerned patients should be counseled to use sunscreens containing the physical/mineral UV filters zinc oxide and titanium dioxide, which are unlikely to contribute to coral bleaching as commercially formulated.7
Ongoing Questions
A lot of unknowns about sunscreen safety remain, and much hubbub has been made over studies that often are preliminary at best. At the time of this writing, absent a crystal ball, this author continues to wear chemical sunscreens; spends a lot more time worrying about their carbon footprint than what type of sunscreen to use at the beach; and believes the association of FFA with sunscreen is unlikely to be causal. Hopefully much-needed rigorous evidence will guide our future approach to sunscreen formulation and use.