After nearly 40 years of SAD eating, I have gone full Paleo close to 3 years. It has resolved many issues: allergies, over-fat, under muscled, flexibility, joint pain, low motility and sperm count, sleep apnea etc. Paleo is some sorta cure all right. It is just too bad my Mother didn't feed me this way from birth. As such, I have a crowded underdeveloped face/jawline/mouth/sinuses as many of us raised on SAD are stuck with.
My mouth breathing is drastically better, other than Paleo nutrition/living, I've incorporated breathe-rite nasal strips, saline nasal washes and just plain focussing on nose-breathing. I have much improvement, but have started to look into more radical measures. I've ceased using steroidal sprays and anti-histamine and other meds.
The various dental appliances, hyrax and others,polyp surgery and other procedures, balloon treatments, chiropractic adjustment and the like all seem promising. None of these are painless or non-invasive. Just can't decide it any of them make much sense.
If you have any experience with other measures, diet related or otherwise, or anecdotal stories to share, please chime in with an answer. I may go down the road of a "simple" run through with a chiropractor first. Then perhaps a hyrax dental appliance. Surgery is lower on the list.