Son 31 Yo Got Out Of The Shower, Not A

Son 31 yo got out of the shower, not a really hot one, and his body turns bright red, with a burning sensation, eyes kinda got big pupils, got somewhat of a rash but not bad. He did not eat anything out of the ordinary during the day. He did take 2 Benadryl about 1/2 hr ago and body is still bright red. He now states his skin is not on fire anymore. He does not have a temp.