system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are some allergies much more common than others?

For example why do a lot of people have peanut allergy?
gpt
Peanut allergy isn't actually that common of a allergy compared to others, its just that generally the reaction is very severe and on a hair trigger. So they are more vocal about it.  They can't just keep it to themselves cause if they get a reaction, It requires their epi pen and a hospital visit.

Someone allergic to cats visiting a cat owner can generally just pop a pill, or toughen it out for a few hours without ever informing the owner.