The one rule: never soak it and never put it in a washing machine. Memory foam is an open-cell structure that holds water in thousands of tiny pockets and cannot be wrung out. Water that gets deep into the foam takes days to leave, and mould grows inside where you cannot see it or reach it. Everything below follows from that.
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What you need
- A vacuum with an upholstery attachment
- Baking soda
- A spray bottle
- Mild laundry detergent or dish soap
- White vinegar
- Two clean white cloths (white so no dye transfers)
- A fan
No steam cleaner, no carpet shampooer, no hose. All three push water into the foam.
The routine clean
- Strip the bed and vacuum the whole surface with the upholstery attachment, including the sides and the seams. Slow passes.
- Sift baking soda over the entire top, a thin even layer. It absorbs moisture and neutralises odour rather than covering it.
- Leave it as long as you can. Minimum four hours, overnight is better, eight hours in a room with the curtains open is ideal. Sunlight through a window helps.
- Vacuum it all off, going over the surface twice.
Do this every three to six months. It is also the right response to a mattress that smells stale but has no specific stain. The sheets above it are on a weekly schedule, set out in how often you should wash your sheets.
Spot-cleaning stains
Blot, never rub. Rubbing pushes the stain sideways and drives liquid deeper.
| Stain | What to use | Method |
|---|---|---|
| Fresh spill (water, drink) | Dry cloth | Press down hard to absorb. Do not wipe. Then baking soda over the damp patch and vacuum when dry. |
| Urine | Equal parts white vinegar and water | Lightly mist, do not saturate. Blot. Cover with baking soda for eight hours, vacuum. Vinegar neutralises the ammonia rather than masking it. |
| Blood | Cold water with a drop of dish soap, or hydrogen peroxide | Cold only. Hot water sets blood permanently. Dab, blot, repeat. |
| Sweat and yellowing | Vinegar solution, then baking soda | Largely cosmetic and rarely comes out fully once set. Prevention beats treatment. |
| Vomit | Remove solids first, then vinegar solution | Then an enzyme cleaner if the smell persists. Enzymes break down the proteins; vinegar alone will not. |
The drying step everyone gets wrong
This is where mattresses get ruined, and it is the part the pages currently ranking for this search skip.
After any damp treatment, the foam needs airflow for far longer than it looks like it needs. The surface feels dry within an hour. The inside is not. Put a fan pointing across the surface, not down at it, open a window, and leave it a minimum of eight hours before putting bedding back on. Overnight is safer.
Do not use a hairdryer on it. Concentrated heat damages the foam structure, and you will have a stiff patch that never recovers its feel.
If the mattress ever gets soaked, a burst hot water bottle, a pet accident that went through everything, be realistic. Foam that wet is very hard to dry all the way through in a home, and a mattress with mould inside it is finished. That is a replacement decision, and the signals are the same ones in how long memory foam mattresses last.
Cleaning a memory foam topper or pad
Same rules, one extra warning: a memory foam topper is not machine washable either, however thin it is. The agitation tears the cell structure and it comes out lumpy.
What you can machine wash is the removable cover, if it has one, and any quilted mattress pad. Which is a different product from a foam topper. The distinction matters and it is covered in mattress pad vs topper. Once it is dry and back on the bed, a fitted sheet over both layers is what keeps a topper from sliding.
Stop doing this every six months
A waterproof protector removes almost all of this work, and it is the cheapest thing in the entire bedroom.
- SafeRest Waterproof Mattress Protector, 4.6 across roughly 280,400 ratings, one of the largest review bases in any bedding category. Fitted, breathable, machine washable.
- Utopia Bedding Zippered Protector, 4.6, ~133,000. Fully encases the mattress, which is what you want if dust mites or bed bugs are the concern rather than spills.
- Quilted Fitted Mattress Pad, 4.6, ~159,400. Protection plus a little extra surface softness.
Ratings read from Amazon on 13 August 2026. How we research.
A protector also extends the life of the foam itself, because body oils and sweat break down the cell structure over years, the mechanism behind most of what happens in the way foam mattresses age compared to hybrids.
