I would really think about throwing this away! But if not, I would use TTB's method then use Odoban to remove any remaining odor. This stuff works great - even seafood odors. - As if you haven't gotten the message - use waterproof mattress protectors & no more problems!.
Thanks everyone for the advice. I'm trying Tipsy's baking soda method and will see how it goes. If the odour comes out, great. If not, I'll replace the mattress ($150 I'd rather not spend).
The mattress cover is a thick, synthetic (polyester? nylon?) material, fully enclosing with zipper. Obviously not waterproof. I hate sleeping on waterproof, but I'll have to get something plastic to use with kids.
Turns out I'm also cleaning four spots on the carpet. The mom stripped the bedding and carried the cot downstairs, and I think the cover is water-repellent enough that some just rolled off onto the floor as she lifted it. Uhg.
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