How old is your husband? Is he taking any meds? Does he have any long standing nagging health issues?
I saw quite a bit of this as a medic in Vietnam. Summer of 06 my wife had a bit of it at the beach.
Heat stroke is NOT good and nothing to take lightly. It can kill you.
However, once the emergency is handled he shouldn't have a problem with heat sensitivity. There's something else going on.
Plenty of water (distilled) and get some good salt going in. Good salt not the store bought kind. Himalayian sea salt is the best. Distilled water.
There's something else going on. In Vietnam once we got the body temp lowered and a little rest the guy was right up at it again. Of course we were all very young at the time. And my wife last Summer was fine after about an hour. Plenty of water and cool the body down. This past Summer was NOT a problem for her. No heat sensativity.
So, there's something else going on. If he's on the meds take a close look at the contraindictions.
Also, check with Barefoot. He might have a few tricks up his sleeve about this. But in general you don't get heat sensativity from heat stroke.