Hi, I Have Developed An Itchy Rash And Hives On

Hi,
I have developed an itchy rash and hives on my armpits. I have tried my prescription of Hyderm Crm 1%, Hydrocortisone Acet 1% on the red patches, and it stings a little at first.... I was prescribed this cream to use for skin allergy on my neck-2 years ago, and it hasn't returned. Should I keep using this cream on my armpits, or is there something else I should be doing?

Thank you, in advance