system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why people catch colds when the seasons change?
gpt
Allergies happen in Spring and Fall due to plants blooming.

Actual colds usually occur in the Winter because people choose to stay inside because it's cold outside.  When people are inside, they're closer to each other.  When people are closer to each other, it's easier for them to share germs, which is why "colds" spread more rapidly in the Winter.