Can excessive alcohol give you A Rash?

Yes. Too much of anything, then sudden drop can give you a rash. Couple of days and certain lotions, it'll be gone. Body has to fix its self all the time.

probably from the antiseptic swab that they clean your arm with, prior to donation.

not necessarily a rash but if you are allergic to the bites they can bite you and cause hives....the hives are red and can appear in clusters. they itch very bad - benedryl otc will help stop the itch

I experience rashes on hands feet for few hours after taking Centrum

No