Sprinkle with dry baking soda, let sit for a while and then thoroughly vacuum.
Mattresses aren’t cleanable unless you’re wanting to spot clean with an enzymatic cleaner, like Nature’s Miracle- which is only good for small amounts of urine, blood & fecal matter.
It will not clean smoke, nor kill pests.
Hi PJ - This article focuses on dust mites, but is an overall great how-to article on how to clean a mattress. Hope this helps! Hugs, Holly