system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does eating spicy food make my nose run?
gpt
It's an inflammation response. Many spicy foods, especially those made with chili peppers, contain an oil called *capsaicin* which is a very powerful irritant to mucous membranes in mammals, such as the eyes, nose, and throat. This is a defense mechanism from the chili pepper plant's perspective, since the GI tract of a mammal would wreck the seeds as they passed through and out. Birds can't taste capsaicin, and along with their relatively gentler digestive system and their ability to fly, the seeds from a chili pepper are much more likely to survive and be spread much farther away. Other spicy foods like horseradish use a different mechanism to produce their spicy taste, but that's a different story.