According to the allergist it is well know by allergists that while on prednsione a nice side effect is that eczema is eliminated but when you stop taking it the eczema returns with a vengeance. She said it is a steroid to avoid if you have a choice and the patient has eczema.
I do not know about psoriasis.
(On the other hand she joked, at prom or wedding time it would be a way to have beautiful skin.....perhaps not completely a joke)
What I do know from experience is when DD was young, before her food allergy diagnosis, we'd be in the ER in the middle of the night with horrible asthma and flared eczema (really a food reaction I think now) and one of the drugs they would give her is prednisone. Then we'd come home with a 5 day regiment. After she'd stop taking it, we'd have weeks of horrible skin that I could not control. Poor thing was still a baby and toddler and I was always at my wits end....not knowing at the time what the prednisone was doing.
That is why I knew to ask about what would happen to her skin on Friday.
Might be worth a call to your DH's doc, or at least you will know a possible culprit if it flares.