Help! Lovely charity shop dress stinks of B.O. and won't wash out!

[alltoomuchrightnow]

Got stunning dress, it looks completely new.
Got it home..this is not the case. The pits stink of BO. It says to wash it cold with detergent. I didn't have time to faff so machine washed it on 30, cold. Still smelt. Re machine washed on 30 delicates (warm). Still smells , of BO and fabric conditioner. The offending areas are stretchy polyester (lycra type). It also has mesh black panel.
What breaks down sweat in fabric but is still kind to fabric?

I got some 'borax substitute' (yeh that's what it's called on box! couldnt get borax and need to sort this out quick) and about to give it a go! but i do have bicarb of soda in the house so maybe should have just stuck to that. will let you know how it goes and thanks for the suggestions!

White vinegar on the arm pits. Wash as usual. Happy days.

Hmm, might be too late to post this caveat but oh well:
boards.straightdope.com/sdmb/showthread.php?t=298322 Read up what they say about borax on there. :)

just read that, thanks. the borax substitute was fine though and no fading, thanks everyone