Labels that read "wash separately," "wash in cold water," "hand wash," "do not use detergent" or "turn inside out to launder" may indicate that the dyes in these items are not colorfast.
To test, soak an inconspicuous corner of the material in a cup of warm water and a teaspoon of detergent for two to three minutes (less time for pre-treatment stain removers; follow instructions on the product label); then blot with a white paper towel. If the colors do not change, run or come off on the paper towel, and if the item is definitely washable, you may safely use Shout products.
Whether you're cleaning comforters, curtains or carpets, always check the care tag first to determine if an item is washable. These days, manufacturers are generous in supplying care instructions. Also, pay attention to the instruction label on your cleaning product; it usually lists fabrics that you should absolutely avoid washing in water.