Ultravate is too strong for regular use on the penis. However, skin thinning is entirely reversible. All you have to do is stop using the Ultravate, let the skin heal for a couple of weeks, and use only moisture lotion. Then you dermatologist (you should consult one) can prescribe a weaker cream for what I assume is psoriasis of the penis, which responds very quickly to weak medications.
Take care.
Dr. Rockoff