system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are people allergic to things?
gpt
The human body is a very delicate thing that hates things from the  outside. Therefore, all the things inside your body have antibodies (like a ticket that shows that they're allowed to be there). Sometimes, the immune system (security guards) don't recognize a ticket and over react. This causes allergies.