I am not too concerned though. I bathe in H2O2 (Hydrogen-Peroxid) (35%), rinse with (3%) and I am not having any problems with it, at all.
OH and I breathe in and out through mouth, or if doing yoga, in the nose and out the mouth (but haven't done that in a while)...TaiChi, also same breathing on some things. Otherwise, breathing is in nose, out nose.