To keep white silk white, add peroxide and ammonia to the wash. To remove yellowing, add 3 or 4 tablespoons of white vinegar to a basin of cool water. Perspiration and sticky deodorant stains can be a problem with any fabric. They are not removable. Use small shields or a silk undershirt.
Some people put their delicate silks in a mesh bag or an old pillow case loosly tieing the open end.
If your silk garment has not been pre-washed some silks may shrink. Also, note that garments made with a combination of fabrics or that are highly detailed probably should not be machine washed. Check with the store where your purchased the item.