Bras will irritate under the arms when the back size is incorrect. It sounds like you are buying a bra in too small of a band size. I believe you said you are a 36--try a size 38 and maybe even move the hook over one time and you may find more comfort.
Eden3000 from San Francisco, CA
This bra is a minimizer and by design it will fit smaller because it compresses the bust for the minimizing\smaller appearance. Try a regular Wacoal full figure bra- we suggest Wacoal Basic Beauty Full Figure Underwire Bra 855192
it will give you the appearance you want and will be more comfortable.
Barbara from Irmo, SC USA
If you are unhappy with this fabric but like the fit please try Wacoal Slimline Seamless Minimizer Bra 85154. It is a great minimizer with a very smooth cup.
Merilee from MD