a strong stomach
1. The ability to eat foods that others may find unusual, unpalatable, or too spicy without experiencing any ill effects like nausea or upset stomach. My husband has such a strong stomach that he can eat a ghost pepper and feel perfectly fine afterward. You must have a strong stomach if you're eating pickles with peanut butter!
2. The ability to experience or witness something unpleasant without becoming upset, nauseous, or squeamish. That horror movie you're going to see is pretty gory. I hope you have a strong stomach! I don't have a strong stomach, so I could never be a surgeon.