Yeah, actually the suggestion was for your grandmother.

Be careful not to blow your nose too hard, Izzy. I recently discovered that there's actually a study out where they used--I forget exactly which type of imaging technique--to observe what happens to nasal mucous when you blow your nose.

Blowing your nose, especially when done forcefully, will often force more mucous up into the sinus cavities than out your nose. That mucous then just becomes a good growth medium for bacteria, which may partly explain why people with chronic sinus infections continue to have lingering or repeated infections. These people are often frequent nose blowers all of the time. I guess they feel that keeping their honker clean all of the time will help prevent recurrent sinus infections. Probably a smart idea, but maybe not the best way to do it. So, other methods like a Neti pot, steam inhalation, maybe this capsaicin nasal spray, drinking lot's of water, is probably healthier because they promote the excess mucous to come out without blowing your nose.

Y'know, in Japan, it is considered impolite to blow your nose in public. In school, you'll have a whole classroom of sniffling kids in the wintertime because they are chastised for blowing their noses. It is also one (of a couple) reason why you see so many people wearing masks, either in the wintertime or during hay fever season in Japan and perhaps the same reason in other parts of Asia. The Japanese don't blow their noses but simply sniffle and let them run so the masks hide that. So, turns out that there may actually be a health reason for that custom after all!

I'm curious, is anyone aware of other cultures where nose blowing is also discouraged?