Cortisone 1% (over the counter). We bought the CVS brand.

However, we hardly used Cortisone for the cradle cap purpose as the cap was all gone after applied with the Baby Oil Gel.  I googled cradle cap, turns out oil does work with it.  I also bought the Gentle Naturals Cradle Cap Care, 4 oz (a shampoo sort of thing) from local Walmart. It worked pretty good. 

The doctor told us cradle cap, he didn't mention 湿疹.