by Quick answer: Blot up fresh urine immediately, then treat with an enzyme cleaner, the only product that breaks down uric acid crystals, which cause the smell. Finish with baking soda left overnight, vacuum it off, and let the mattress dry completely before remaking the bed.
By the MattressNut editorial team · Updated June 2026
Why Urine Smell Lingers (And What Actually Fixes It)
Urine odor is stubborn because it comes from uric acid crystals left behind as the liquid dries. Regular soap and water don't break those crystals down, they just push moisture deeper. Enzyme cleaners are different: the enzymes digest the uric acid at a molecular level, which is why the smell doesn't come back after a proper treatment. For memory foam mattresses specifically, use as little liquid as possible; foam absorbs moisture quickly and is slow to release it.
Fresh Stain: Step-by-Step Method
Act fast. The less time urine has to soak into the foam or fibers, the easier the cleanup.
- Blot, don't rub. Press dry towels firmly onto the wet area to pull moisture up and out. Rubbing spreads urine sideways and deeper.
- Apply enzyme cleaner or a vinegar solution. Spray an enzyme cleaner made for urine or pet odor until the area is saturated, enough to reach as deep as the urine went. If you don't have enzyme cleaner, a 1:1 mix of white vinegar and water is a reasonable first step (it neutralizes odor but won't fully break down uric acid crystals).
- Let it sit. Follow the enzyme cleaner's label time, usually 10-15 minutes. Don't rush this step.
- Blot dry again. Press clean towels onto the treated area to lift the cleaner and the broken-down compounds.
- Cover with baking soda. Spread a generous layer over the spot. Leave it for several hours or overnight, it draws out residual moisture and absorbs any remaining odor.
- Vacuum and dry. Vacuum up the baking soda, then aim a fan at the mattress and leave it to air-dry fully before putting sheets back on. Skipping full drying is the most common reason odor returns.
Set-In or Dried Urine
Old stains need a different approach because the uric acid crystals have fully dried and bonded to the fabric. Lightly dampen the stained area with water first to rehydrate the crystals, then apply enzyme cleaner generously and let it work longer than the label minimum.
For stubborn set-in stains, a paste of hydrogen peroxide, baking soda, and a drop of dish soap can help lift what the enzyme cleaner loosens. Test a small hidden patch first, hydrogen peroxide can bleach some mattress fabrics. Apply, let sit 15 minutes, blot, and follow with the baking soda step.
Very old, deep-soaked stains may not fully clear no matter what you use. At that point, the question becomes whether replacing the mattress makes more sense than continuing to treat it.
Preventing Recurrence
A waterproof mattress protector is the single most useful thing you can add after cleaning. It sits between the sheet and the mattress and catches any future accidents before they reach the foam. Look for one that's waterproof but still breathable, some cheap versions trap heat and make sleeping uncomfortable.
Make sure the mattress dries completely after any cleaning. A fan directed at the surface for several hours is enough in most cases. Putting sheets on a damp mattress seals in moisture and creates the conditions for mold and mildew, which carry their own smell.
If the mattress is already old and sagging, or the odor won't fully clear, a replacement is worth considering. Our Saatva mattress review covers one solid option that comes with free removal of your old mattress. See the Saatva Classic.
Frequently Asked Questions
Does baking soda alone remove urine smell from a mattress?
Baking soda absorbs odor and draws out moisture, but it doesn't break down uric acid crystals. It works best as a finishing step after an enzyme cleaner has done the main work. Using baking soda alone on a set-in stain will reduce the smell temporarily, but it usually comes back.
How long does it take for urine smell to go away after cleaning?
After a full enzyme-cleaner treatment and a baking soda soak, most fresh stains stop smelling within 24 hours once the mattress is fully dry. Set-in stains may need a second treatment or a longer dry time. If the smell lingers after two proper treatments, the urine likely soaked deep enough that it's difficult to fully eliminate.
Can I use vinegar to get urine smell out of a mattress?
White vinegar (diluted 1:1 with water) neutralizes some of the alkaline compounds in urine and can reduce fresh odor. It doesn't break down uric acid crystals the way enzyme cleaners do, so it's a decent stop-gap when enzyme cleaner isn't available, but not the most thorough fix for anything beyond a very fresh stain.
Is hydrogen peroxide safe to use on a mattress?
A diluted solution (3% hydrogen peroxide, which is the standard drugstore concentration) is generally safe on most mattress fabrics when used sparingly. The main risk is discoloration, always test a small hidden area first. Don't use it on memory foam repeatedly, since excess liquid is hard for foam to release and can promote mildew.
What is an enzyme cleaner and which one should I use?
Enzyme cleaners contain biological enzymes that digest organic matter, urine, pet waste, vomit. Brands like Rocco & Roxie, Nature's Miracle, and Biokleen are commonly used for mattress cleaning. Look for one labeled for urine or pet odor rather than a general-purpose cleaner. Apply enough to saturate the stained area, and follow the label's dwell time.
Can urine smell come back after cleaning?
Yes, if the uric acid crystals weren't fully broken down or the mattress didn't dry completely. Moisture reactivates the remaining crystals and the smell returns. This is the most common reason a cleaned mattress still smells after washing. A second enzyme treatment, longer dwell time, and complete drying usually resolves it.
The Bottom Line
Enzyme cleaner breaks down uric acid crystals, the root cause of urine smell, where regular cleaners can't. Blot first, saturate with enzyme cleaner, finish with baking soda left overnight, and dry the mattress fully before remaking the bed. For set-in stains, dampen the area first to rehydrate the crystals, then treat. A waterproof protector prevents the next accident from becoming the same problem.