Urine odors can be removed from a mattress with Borax, water, a sponge or brush, and a vacuum cleaner. Borax neutralizes urine odors in a mattress in only an hour, and it can be found in the laundry aisle of most grocery stores.
To remove urine odors from a soiled mattress, dampen the stain with water using a spray bottle. Sprinkle borax over the dampened area, completely covering the stain. Work the borax over the stain using a brush or a sponge, dampened a bit if necessary. Allow the borax to dry completely. It takes at least an hour for the borax to turn back into a powder. Then, vacuum the borax off the mattress.