Red bumps appear

So I know this might be TMI but I am hoping someone has experienced this before and has advice! My fiancé will cum on my breasts and chest and if it stays there for a little while red bumps appear as if I’m allergic to it. I googled it and some people actually are allergic to sperm but I’ve never heard of this before!! It has us worried about having trouble conceiving some day. Any one who has experienced this please let me know!