Proactive testing for allergy to a medicine as a baby?

DS #2 may decide to apply to service academies/ROTC, he is entering Junior year. A question: being through it all with DS #1, a '22 appointee, I am wondering if it makes sense to try and remedy a diagnosis that we had with him as an infant. An 'allergy' or 'reaction' to amoxicillin. At the time, he had a reaction to both amoxicillin and zithromax, but has since had zithromax and not reacted. So im wondering if that will also be an issue.

Any advice? Im trying to be proactive. I also...

Proactive testing for allergy to a medicine as a baby?