best way to get white marks from anti-persperants off black clothes

[treacletart]

I've got some nasty shiny white marks on the underarms of a black dress - could be deodorant could be sunscreen or both? standard 40degree wash didnt get them out. Any tips?

I have heard (don't know how good it is) that a paste of bicarbonate of soda and water smeared on and left for a while could help.