system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what are Canker sores and why do they hurt so bad?
gpt
Canker sores are small sores (which is like a cut or opening) on the inside of your mouth, interestingly we are not quite sure why they appear although they seem to come more when people are stressed, with a certain ingredient in some toothpastes, and seem to run in family's (but are luckily not contagious). They hurt so much because the area becomes inflamed which means puffed up with blood so your body can heal it, sometimes your nerves which are what make you feel pain confuse the puffiness and pressure with more damage to the area.