The law of unintended consequences contends that positive and purposeful actions always have unanticipated effects. This law has been made malodorously clear over the past six months. Wearing a face mask to prevent the spread of the coronavirus – an unambiguously positive action – has revealed to many of us our own bad breath.

The mask itself is not causing or exacerbating bad breath, says Dr. Melissa Santilli, a dentist in Cross Roads, Texas. “Mask-wearing is just making many become aware of it. The bad breath has always been there,” she says.

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