Its worse than it sounds, because semen doesn’t really exist in you body until it’s about to be used. Its not a problem until sexytimes, and can ruin it altogether.

Imagine masturbating for the fifth time ever, and start going anaphylactic. You find out whether you like autoerotic asphyxiation real quick…

Allergies like that tend to be external in nature. Like how people can be allergic to water.

Your body freaks out when something comes into contact with it externally but internally it’s fine.

The line between the two can be less then intuitive tho. Not everything inside your body is “internal” in this context.