On herceptin and perjeta , stage 4 , itchy skin and now itchy scalp -anyone treated itch sucessfully

I would love suggestions to control the itch. Finished 18 rounds of herceptin and perjeta on 1st March  The itch is insane. I have welts all over both forearms. Im using loratadine, dexmethasone, promethazine, ice packs, steroid cream, moo goo and lipikar ar. Contacted oncologist - was told someone would get back to me in the next week or 2! Contacted breast care nurse - still waiting on a response. GP is booked out until Friday 12th May.