L.L.
Eliminating foods did nothing for us, but what did help was Johnson's Creamy Baby Oil, and prescription cream called mometasone, and only bathing once every 4-5 days with spot cleaning in between.
I've dealt with this for almost 6 years with my oldest, and my newest daughter has it too. Nothing else worked for us...Aquaphor almost seems to make it worse, as did every other thing my doctor suggested over the counter. Honestly, though it isn't recommended, the creamy oil was the best...slather on a ton of it...and the mometasone is similar to a cortisone cream.