It's 2am, the bed is soaked, and you need this sorted before morning. Here's what actually works, in the order to do it.
Act fast and most mattresses recover completely. Leave it and the uric acid crystallises, which is what causes that ammonia smell to come back every time the room warms up.
Right now: the first five minutes
- Strip the bed. Sheets, protector, everything. Straight into the machine on a hot wash.
- Blot, don't rub. Press down hard with a towel and keep going until it stops lifting moisture. Rubbing pushes urine deeper into the foam, which is the single most common mistake.
- Don't soak it. Whatever you use next, damp is enough. Over-wetting a foam mattress causes mould that's far harder to deal with than the original problem.
The method that works
Step 1. Mix equal parts white vinegar and cold water in a spray bottle. Mist the area until slightly damp. The acid breaks down the alkaline compounds in urine, which is why vinegar works where soap doesn't.
Step 2. Leave it 10 minutes, then blot with a dry towel.
Step 3. Cover the damp area generously with bicarbonate of soda. It should look like snow. Leave it as long as you can, ideally overnight, and at least four hours.
Step 4. Vacuum it all off with the upholstery attachment.
Step 5. Repeat if you can still smell it. Dried-in accidents often need two or three passes.
If the smell keeps coming back
That means uric acid crystals are still in there, and vinegar alone won't shift them. Use an enzyme cleaner, which is the only thing that genuinely breaks the crystals down rather than masking them. Available from most supermarkets and pet shops. Follow the label, and let the mattress dry fully before making the bed.
Avoid bleach entirely. It damages the fabric, can degrade foam, and doesn't touch the uric acid.
Drying it properly
This is where most people undo their own work. Open a window, get a fan on it, and don't put bedding back until the mattress is dry all the way through. Press a dry towel into the area and check for damp. On a foam mattress allow a full day.
Bunk beds and high sleepers: a word of warning
If the accident is on a top bunk or high sleeper, don't try to clean it in place. Water running down into the frame is a genuine problem, and reaching across a guard rail with a spray bottle is how people fall.
Take the mattress down to the floor, clean it there, and let it dry flat before putting it back. Awkward, but far better than the alternative.
When a mattress can't be saved
Sometimes it's beyond cleaning, and it's worth knowing when to stop. Replace it if:
- The smell returns every time the room warms up, after two or three thorough cleans
- There's visible mould or dark staining under the cover
- Accidents have happened repeatedly over months and it's been soaked through more than once
- It's more than seven or eight years old anyway
There's no reward for saving a mattress your child is sleeping on unhappily. If you're at that point, our kids' mattress range starts at 15cm deep, which is the correct depth for bunk beds and high sleepers where guard rail height matters. Everything is made in the UK and arrives rolled, so it comes upstairs easily.
Stopping it happening again
Two levels of protection, depending on how often you're dealing with this.
Occasional accidents: a waterproof protector
A waterproof mattress protector sits between the sheet and the mattress and takes the hit instead. It goes in the washing machine, the mattress stays dry, and you're changing bedding at 2am rather than cleaning foam.
If you buy nothing else after reading this, buy one of these. They cost a fraction of a mattress.
Regular accidents: a waterproof mattress
During potty training or a bedwetting phase, a protector alone can struggle. A heavy accident finds the edges, and you're back to cleaning the mattress underneath.
The DryComfort 15 is built for exactly this. The whole mattress is waterproof, not just a cover laid over the top, so nothing reaches the foam at all. Wipe it down, remake the bed, done.
It's a proper mattress underneath, with a reflex foam comfort layer over a supportive base, and at 15cm deep it fits bunk beds, high sleepers and trundles. Made in the UK, in eight sizes from shorty to double.
The practical stuff
- Double-layer the bed. Protector, sheet, second protector, second sheet. At 2am you strip one layer off and there's a made bed underneath.
- Last drink an hour before bed, and a final toilet trip as part of the routine.
- Keep spares to hand. A clean set of bedding in the room means five minutes rather than twenty.
And worth saying plainly: bedwetting is normal well into primary school and it isn't anyone's fault. If it's causing real worry, your GP or health visitor will have seen it a thousand times.
Keeping on top of it
- Monthly: vacuum the mattress, sprinkle bicarbonate of soda, leave an hour, vacuum off.
- As needed: spot clean using the method above.
- Annually: a deeper clean, and check the mattress is still supportive and within its useful life.
More on this in our guide to cleaning a mattress properly.
Common questions
Can I use bleach?
No. It damages the fabric, can break down foam, and doesn't remove the uric acid causing the smell. Vinegar, bicarbonate of soda and enzyme cleaner are what work.
Why does the smell come back when the room is warm?
Uric acid crystals left in the mattress reactivate with heat and humidity. It means the cleaning didn't reach them, and an enzyme cleaner is the answer.
Can I clean an old, dried-in stain?
Usually. It takes longer and often two or three passes. Start with the enzyme cleaner rather than vinegar, since the crystals have set.
Is a memory foam mattress harder to clean?
Yes. Foam absorbs faster and dries slower, so use less liquid and allow a full day of drying. Never soak it.
Should I get a protector or a waterproof mattress?
A protector for occasional accidents. A waterproof mattress like the DryComfort 15 if it's happening regularly, or if you'd rather not think about it at all.
How often should I clean my mattress?
Vacuum and deodorise monthly, spot clean as needed, deep clean once a year.
