Usually there are only a couple of things that can make your wedding dress smell funny. The first is when its brand new and “fresh” from the bridal store.
Since almost all wedding dresses are made in China and then shipped to the U.S. they must be chemically treated in China. This treatment is to keep unwanted insects from being accidentally transported with the wedding gowns. So they are chemically treated to kill these insects. The insects won’t be in the wedding dress itself, but will have gotten a free ride on the outside of the shipping bag.