Off Herceptin and developed ITCHY rashes

[mts]

I completed 1 year of Herceptin in July and I have developed large itchy patches of skin on several parts of my body. Under my armpit, around my neck, inside of elbow... Onc suggested I go to a dermatologist and he prescribed Benadryl tablets and calamine lotion. The benadryl helps at night (I can't take during day because it makes me really sleepy). I don't think that dermatologists are really "with it" when it comes to Herceptin...
Anyway, is anyone having rashes that don't seem to go away, and if so, what are you taking?
This is driving me crazy!

Maria (MTS)