If a fabric softener is poured directly on an item, it may leave a stain. The stains will vary in color depending on the softener used, or it may be a gray color if it has attracted soil from the laundry. These stains are easy to remove. Simply dampen the area, rub it with a bar of soap and relaunder the item. Mild alkaline products such as toothpaste, perspiration, and facial soaps, or acidic products including deodorants, and hair sprays, are often to blame for unknown stains.
Perfumes contain alcohol so they are often responsible as well.
Even rain can leave spotty stains if it has picked up impurities from the air. All of these may dry invisible, but age and exposure to heat will cause them to become visible. There are many stain removal solutions that people may believe in. Some may work, and some may not. Club soda may be useful if applied immediately before a stain has time to set.