Medical and public health professionals recommend wearing face masks to combat the spread of the coronavirus disease of 2019 (COVID-19). While the majority of people in the United States support wearing face masks as an effective tool to combat COVID-19, a smaller percentage declared the recommendation by public health agencies as a government imposition and an infringement on personal liberty. Social media play a significant role in amplifying public health issues, whereby a minority against the imposition can speak loudly, perhaps using tactics of verbal aggression taking the form of toxic language. We investigated the role that toxicity plays in the online discourse around wearing face masks. Overall, we found tweets including anti-mask hashtags were significantly more likely to use toxic language, while tweets with pro-mask hashtags were somewhat less toxic with the exception of #WearADamnMask. We conclude that the tensions between these two positions raise doubt and uncertainty around the issue, which make it difficult for health communicators to break through the clutter in order to combat the infodemic. Public health agencies and other governmental institutions should monitor toxicity trends on social media in order to better ascertain prevailing sentiment toward their recommendations and then apply these data-driven insights to refine and adapt their risk communication messaging toward mask wearing, vaccine uptake, and other interventions.