Sometimes, silk smells so terrible as to be unwearable. My nose forcibly reminded me of this recently when shopping for materials from which to knit a present for a friend who is--sadly but truly--allergic to wool.
Silk's terrible smell problem evidently comes from a gum left in the raw fiber as you can read here. In my experience, that silky - fishy smell never comes out, regardless of what you may try; not drycleaning, not sprinkling with baking soda, not detergent, not airing outside for days on end. (Not to mention--washing is hard on silk--silk has "low wet resiliency," meaning it is weak when wet, and easily crinkled.) Some method or another may have you convinced that you've got the problem knocked back a little, but as your body heat warms the silk, the smell may very well return. And if a silk garment with that fishy smell ever gets wet while you're wearing it ... rip the garment off and flee before sea gulls start circling.
Moral of the story: best to buy silk when you can touch and smell it. Go shopping on a day when you don't have a cold, and your allergies aren't acting up, and/or take a friend with you who has a keen sense of smell. Sniff, sniff, sniff before you buy. If you must purchase by mail order or off the web, be SURE to ask about the return policy. At the price of silk, there is no reason to buy yourself a lot of trouble vainly trying to get the smell out of an otherwise gorgeous silk garment--and of course, this is true of ready-made silk garments too.
Last note: the price does not guarantee no smell. Of three selections in my LYS, the cheapest was the only odor-free brand, the most expensive had a distinct punge, and the middle price range--which came in the largest selection of colors--smelled like fish bait.
Addendum the first: Thanks to the knowledgeable comments of June, here is a link to a site (called "wormspit!!") which shows a serious method of smell-elimination. If you already have a smelly silk problem, you could try this, although the link speaks only of undyed silk, and so may not be the thing for an already made up garment. The sophistication of this process shows again how very important it is to smell BEFORE you buy, or you may find yourself playing junior chemist...
Addendum the second-- Michael of wormspit came to visit! (Hi Michael!) Be sure to read what he has to say--he has the real low-down on all the different ways silk can come to smell bad--his wisdom is in the comments below.
(You have been reading TECHknitting on: smelly silk)