What Causes Small Red Bumps And Patches In The Lower Arms , Armpit And Breast?

i have broken out in a rash small red bumps in large clusters/patches, started in the crease of my lower arms and has spread to armpit, creases in back, under breasts, buttocks and inner thigh groinal area. I have been using a canestan cream with no effect. Its so itchy i feel like tearing my skin off!