Hello, Welcome on Healthcare Magic! I understand your concerns. Normally when someone is allergic from Penicillin, the next first choice it is Erythromycin or Azithromycin for respiratory tract infections. And this is the case of your husband. Some people are really sensitive from side effects of Azithromycin, some others not at all. If your husband can tolerate the side effects (because you are saying that they are not related with skin or respiratory tract), I think you should not be concerned. But if the side effects are serious ( each leaflet of drugs divide the side effects in some category) and interrupt the daily activity, you should go to the doctor who prescribed that to switch to another medication. I hope my answer was helpful to you! Best Regards! Dr Eniola