Natto. Literally the worst, IMO. Even a good number of Japanese folks don’t like it.

This is called the nasal cycle.

Use Flonase to help (need daily use for >= 4 weeks) If this doesn’t help enough, you should see an ENT.

Fun fact: the turbinates in the nose (which are responsible for the nasal cycle) have erectile tissue in them.

Source: your friendly neighborhood Otolaryngologist