How do you test for tetanus before you get booster if you think you are allergic?

Skin test: One can always do a scratch test to see if there is an urticarial reaction (hives). Most aren't allergic to this, and i don't know what has led to the thought if it's allergic, but a visit with an allergist to test may be the best option. If there's a question or a concern that there could be an allergy but you're not sure, sometimes you can get the shot at the allergist.