My recollection is that there is little to no research on mouth taping, and the patient populations that are specifically cautioned against it are those with heart or lung disease, gerd, sleep apnea. Low oxygen levels was one stated concern, I don’t recall the others off the top of my head but I do recall googling it and finding enough information to give me pause. I did read that sleeping position may matter, with sleeping on back or stomach viewed as possibly contributing to the mouth breathing, while sleeping on side was seen as potentially helpful. I try sleeping on side, for a variety of reasons, but always end up flat on my back. In general the medical consensus seems to be that one should find the reason they are mouth breathing and address the root cause. Again my dentist told me that my mouth breathing has to do with the structure of my sinuses which makes it harder to breath comfortably through my nose. His fix was to refer me to a specialist to crack open and widen my palate, among other things. It seemed kinda crazy at the time, but again that was before all the BE/MAC started and now the value of improving my nose breathing seems higher to me. I definitely need to get a 2nd (maybe 3rd) opinion.