I have had psoriasis since I was 13, and reasonably severely and I have never had a problem with fertility. I think your GP is making some massive assumptions and honeslty I would go with the dermatologist on this. I use both Elocon lotion and cream and they do work a treat - I have also continued to use them during pregnancy as well as they are a topical treatment and will not affect a baby and therefore they should not affect his sperm when TTC. In-Liven is a fantastic probiotic as well. It is an auto immune disease, which means that our immune systems are hyperactive so to speak and work much faster than a person's who doesn't have it. TBH, I would be looking at other causes for his sperm issues. By all means getting his p under control can't do any harm, but I think the FS will be able to shed more light on it for you.