Face masks for the public during Covid-19: an appeal for caution in policy

As the Covid-19 crisis deepens, some researchers have argued for the widespread routine use of face masks in community settings, despite acknowledged gaps in the evidence base for the effectiveness of such a measure. We argue that such calls are premature, and risk neglecting important potential harms and negative consequences, known and unknown. We identify potential unintended consequences at multiple levels, from individual-behavioural to macrosocial, and suggest that it is far from clear that the benefits of widespread uptake of face masks, whether encouraged or enforced by public authorities, outweigh the downsides. Finally, we make the case for caution in communicating unequivocal messages about the scientific evidence for face mask use to policy, practitioner and public audiences, given continued scientific disagreement on the question.