Nature's miracle works great on carpets. It will likely work on mattresses too. Just make sure you don't try to clean the spot first with other products or it won't work. Sponge up any wetness you can with paper towels and then pour on the product and let it soak in and dry for a few days. Repeat if necessary.

Try to avoid the scented product as you won't like the scent on your mattress . Or carpet for that matter.