Iron Infusions/Side Effects

Hello, I received my first of two iron infusions last Friday. Afterwards I felt like Popeye. A couple of hours later I broke out in a terrible rash which was unexpected. However, my hematologist has suggested I take benadryl before this Friday's infusion. The nurse at the infusion center did inform me that I might feel rather "flu like" for a couple of days following the infusion. While I am not usually one to complain about much, I was sicker than a dog all weekend. The symptoms reminded me of how I felt after getting one of my COVID-19 vaccinations. Has anyone else had these reactions after an iron infusion, or are these symptoms a fragment of my imagination?

I am unable to take oral iron supplements because they cause terrible stomach upset, the details of which I will withhold. Even the slow release ones do not help me.