Masks are incredibly harmful because they lower oxygen levels in the blood (leading to hypoxia) while raising carbon dioxide levels (leading to hypercapnia), and force you to inhale and exhale more forcefully, stressing the cardio-pulmonary system. This is especially dangerous for the elderly.
Even doctors who wear surgical masks do so to prevent them from drooling into a patient’s wound, not to protect them from pathogens, and hospitals are required to increase oxygen levels to compensate for the loss of oxygen in the mask. There’s an entire body of OSHA regulations that requires that workers be tested to see if they’re fit to wear a mask and for how long—it’s dangerous stuff and can cause dizziness, fainting, and headaches.