Just wanted to thanks everyone for their input here, especially those than mentioned the aluminium based deodorants being a problem.
I've since purchased a couple of organic ones, one tea-tree oil based that I really like. No stains, no residual smell....and the deodorants actually work a shitload better...I wore some out to a movie and drinking night, then went to sleep in the shirt after a hot night...and NOTHING. Great stuff.
Anyways, thanks for all the advice people.