Hi birdlady, it can be allergy, but it can also be healing reactions.

I wonder if you are allergic to supplemental zinc and vomiting maybe a sign of this. So if you don't vomit, maybe your body instead throws up hives. Again healing reactions can be the same as allergic, so it's very hard to tell.

Perhaps you could drop the zinc and see if things settle. Then try it again and see if the same problems occur. But again, it maybe healing. Also when toxins come out onto the skin, they can cause skin reactions similar to this. When metals were coming out onto my skin, I was hot, covered in rashes and itching. This worsened when heating up/exercising/hot baths.