Unknown source symptoms and conditions

Was prescribed Sulfamethoxazole-Trimethoprim 3 days ago for a bacterial skin infection. At the same time, I also had an apparent allergic reaction going on (unknown source, had never had one before) where my arms were both covered with hives/welts. So my skin was peeling and hive covered BEFORE even starting the meds, which is making the evaluating of the drug side effects a bit trickier. So far, the skin seems to be improving but the hives/rash has not improved, despite taking prescribed allergy meds during the same time. So this could be the current source of the rash, but I can't tell.
On the plus side, have not had any stomach upset (I took all doses w/ food) or other GI symptoms other than increased frequency in BMs. I only seemed to get a headache after not drinking water for a couple of hours. If online sources are to be believed, the "sulfa" portion of this is the culprit behind the worst side effects, AND food may interfere with absorption/effectiveness. Based on that, I'm planning on taking my remaining doses w/ food since the skin infection is already clearing up after 2 days and I've got 10 days to go. Hoping to avoid the reactions folks described here where they starting rashes late in the treatment cycle.

My husband developed hives from an unknown source. They have put him on prednisone now twice. His side effect is ANGER. He has been dizzy, hungry and angry. I am hoping they can identify his allergen soon to get him off this stuff. He was taking the tapering dose of 6 5mg pills per day tapering down to zero.