Never Blow Your Nose
Source: https://www.verywellhealth.com
If you happen to be under the weather and experiencing a runny nose, whatever you do, never blow your nose in public or in front of other people, even if you’re not in a dining area. Doing so is considered rude in Korea, so before it gets out of hand, excuse yourself and retreat to the toilet or restroom. If it’s not possible, just make sure there’s no one around. Don’t forget to have a tissue with you so you can dab your nose with it.