Mattress mould; Why it happens and how to treat it

Mattresses kept directly on the floor

You will often see the initial signs of mould on mattresses that are kept directly on the floor or on cheaper solid top bases. This is because the mattress underside gets zero ventilation, meaning that any moisture can build up, leading to mould.

This is also why some short-term rental properties end up with mattress mould: mattresses can be left for months without maintenance or ventilation. It is the build-up of heat and moisture that then enables mould to thrive in this scenario.

How often have you stayed somewhere short-term and thought, ‘I’ll turn the mattress and open the window’? Probably not often! We always recommend you turn your mattress monthly, which should help keep any potential mould problems at bay. Remember, it’s only in rare cases of high humidity and lack of ventilation that mould takes hold.

Why Memory Foam Traps Moisture (And Natural Fibres Don’t)

You’ll notice we mention memory foam being prone to mould. When people contact us about mouldy mattresses, which, believe me, is often, it’s 9/10 times about a memory foam bed. Here’s exactly why that happens.

Memory Foam Doesn’t Breathe

Memory foam is designed to trap heat and mould to your body. That same property means it doesn’t allow airflow. Over 8 hours of sleep, your body releases about half a pint of moisture through perspiration. In memory foam, that moisture has nowhere to go.

It gets trapped in the foam layers, creating the perfect environment for mould spores. Even with a mattress protector, the moisture still accumulates inside the mattress itself.

Natural Fibres Work Differently

British wool, cotton and horsehair are naturally breathable materials. Wool can absorb up to 30% of its weight in moisture without feeling damp. That moisture gets wicked away from your body and released into the air around the mattress.

This is why you rarely see mould on traditional pocket spring mattresses with natural fillings. The combination of airflow through the springs and moisture-wicking natural fibres prevents the conditions that mould needs to grow.

Wool’s Natural Protection

British wool contains lanolin, which naturally repels mould and mildew. It’s not marketing; it’s chemistry. Shepherds have relied on this for centuries.

This is one reason we use British wool in our mattresses. It’s worked for generations because it solves real problems like mould and overheating.

Memory foam mattresses require extra vigilance with ventilation and turning because the material itself can’t help regulate moisture.

What to do if your mattress develops mould?

If your mattress does develop mould, then there’s no need to panic; it can be removed by following the mattress maintenance steps below.

• You would first need to vacuum both sides of the mattress thoroughly. Even on a non-turnable mattress, it’s advisable to thoroughly vacuum both sides. Once you have done this, ensure that you fully empty your vacuum in order to prevent any further spread of the mould.
• Using warm soapy water, deploy a circular motion to clean the affected area with a damp cloth. Ensure that you don’t soak the cloth that you’re using as this will only exacerbate the situation by adding further moisture to the area.
• Once this is done, allow as much air to the mattress as you can in order to let it dry and ventilate. The ideal way to do this is to allow direct sunlight to the mattress. If this can’t be done, just allow as much air as possible to it.

Mould on a mattress is a product of the environment in which it is kept and is not caused by the mattress itself.

How to prevent getting a mouldy mattress

If you have a mouldy mattress, then the chances are that it’s been a lack of mattress maintenance that caused the mould. Mould can only exist where there is humidity, dust and warmth in the bedroom. These are all things which you can easily avoid with mattress care.

Mould thrives on organic matter and breaks it down, leading to mould growing and spreading. This is usually down to dust and dead skin. Also, if there is a high level of humidity and other organic compounds found, then mould can appear on your mattress. This combination would cause any piece of furniture to develop mould and mildew.

We recommend that you rotate your mattress monthly, not only to ensure even settlement, but to ensure there’s adequate airflow around the mattress.

By doing this, you will highlight any potential mould issues as well as allowing the mattress to ventilate evenly: particularly where the mattress is on a solid top base. All of our mattresses have side handles, enabling much easier turning.

If you don’t turn your mattress frequently, this can result in uneven settlement in your mattress, where lumps and bumps may form. This is because you’re not evening out the wear of the internal fibres of the mattress on both sides.

Ensuring that damp clothes/towels are not dried in the bedroom or near the bed will help too, and leaving a window open slightly to help air circulate is also recommended with any bed if there is humidity in the room. General hygiene, cleaning up spills and keeping bed linen clean and dry will also help prevent this.

• Ensure adequate airflow in your bedroom
• Avoid drying clothes in the bedroom
• Clean up spills ASAP on mattresses and beds
• Pull your covers back for an hour when you get out of bed to help it air

If you’re looking for more mattress help and advice, why not check out our ultimate guide below? It could save you a fortune when you next buy a mattress.

UK Humidity Control: Stop Mould Before It Starts

Mould needs three things to thrive: moisture, warmth, and poor ventilation. UK homes are particularly vulnerable because we seal everything up tight against the cold. Here’s how to break the cycle.

Target Bedroom Humidity: 30-50%

Most UK bedrooms sit at 60-70% humidity in winter. That’s mould paradise. You need to get that number down to 30-50% consistently.

Invest in a hygrometer (£10-20 from Argos or Amazon). Stick it on your bedside table. When it reads above 50%, you need to take action.

Ventilation Even in Winter

This feels counterintuitive when you’re trying to stay warm, but it’s essential. Crack open a window for 10-15 minutes every morning. Yes, even in January.

The brief cold is worth it. You’re exchanging damp, stale air for fresh, drier air. Your mattress will thank you.

If you’ve got trickle vents on your windows, use them. They provide constant airflow without freezing you out.

Dehumidifier Recommendations

For chronic damp problems, a dehumidifier is a game changer. Position it in the bedroom overnight and empty the water collection tank daily.

You don’t need anything fancy. A 10-12 litre capacity model handles most UK bedrooms perfectly. Run it until the room reads 40-50% on your hygrometer, then you can ease off.

Never Dry Clothes in Your Bedroom

We know space is tight, especially in flats. But drying laundry in the bedroom pumps massive amounts of moisture into the air. One load of washing releases 2 litres of water into the room as it dries.

If you must dry indoors, use the bathroom with the door closed and extractor fan running, or get a heated clothes airer with a cover.

Check Your Base

Solid divan bases trap moisture underneath the mattress. If you’ve got a solid base and recurring mould problems, consider switching to a slatted bed frame. The airflow underneath prevents moisture buildup.

Keep at least 10cm clearance between your mattress and the floor if using a platform base. Air needs to circulate freely on all sides.

5 Proven Methods to Remove Mattress Mould

If you’ve caught the mould early, these methods can save your mattress. We’ve spent 25 years advising customers on mattress care, and these are the treatments that actually work.

Method 1: UV Sunlight Treatment (Our Top Pick)

Cost: Free
Effectiveness: Excellent for surface mould

Strip your mattress and get it outside on a sunny day. Direct sunlight kills mould spores naturally through UV radiation and dries out moisture that caused the problem in the first place.

Leave it for 4-6 hours minimum, rotating every couple of hours so both sides get treated. This works brilliantly for early-stage mould and costs you nothing.

Yorkshire tip: Even our grey skies have UV radiation. If you can’t get proper sunshine, position the mattress near an open window with maximum airflow.

Method 2: White Vinegar Solution

Mix: 1 part white vinegar to 1 part water
Effectiveness: Kills 82% of mould species

Pour the solution into a spray bottle and saturate the affected area. Don’t be shy with it. Let it sit for an hour, then scrub with a stiff brush. Blot with clean towels and let it dry completely.

The vinegar smell disappears once dry. Open windows and use fans to speed up drying time. Never sleep on a damp mattress or you’ll be back to square one.

Method 3: Baking Soda + Vinegar Combo

Best for: Stubborn mould with odour

Start with the vinegar treatment above. Once the area is dry, sprinkle baking soda liberally over the treated spot. Leave it for 8-12 hours or overnight. The baking soda absorbs lingering moisture and neutralises any remaining smell.

Vacuum thoroughly with an upholstery attachment. This one-two punch deals with both the mould and the musty odour.

Method 4: Rubbing Alcohol Method

Concentration: 60-90% isopropyl alcohol
Effectiveness: Excellent penetration

Spray rubbing alcohol directly onto the mould. It evaporates quickly, so there’s less risk of adding more moisture. Let it sit for 15 minutes, scrub with a brush, then blot dry.

Rubbing alcohol penetrates deeper than water-based solutions, making it useful for mould that’s got a bit of a grip. Work in a well-ventilated room because the fumes are strong.

Method 5: Hydrogen Peroxide

Concentration: 3% solution
Caution: Test first on hidden area

Hydrogen peroxide kills mould and lightens stains, but it can also bleach fabric. Always test on a hidden corner first. If your mattress cover is dark coloured, skip this method.

Spray onto the mould, leave for 10 minutes, scrub, then blot dry. This is your nuclear option for visible black mould that hasn’t penetrated too deeply.

When Your Mattress is Beyond Saving

Sometimes cleaning won’t work. Here’s when you need to replace the mattress.

Mould Larger Than a Dinner Plate

If the mould patch exceeds 25-30cm in diameter, it’s likely penetrated deep into the core. Surface treatments won’t reach it all. The spores are throughout the mattress structure.

Replace it. Your respiratory health isn’t worth the risk.

Black Mould Anywhere on the Mattress

Black mould (Stachybotrys) is the dangerous variety. It releases toxins that cause breathing problems, headaches and worse.

Don’t attempt DIY treatment. Get a professional mould assessment if needed, and replace the mattress immediately. Sort out the underlying damp problem too, or your new mattress will go the same way.

Visible Mould on Both Sides

Mould on the top is manageable. If you flip it and see mould on the underside too, it’s gone right through. Game over.

This indicates serious moisture problems beyond just the occasional spill. You’ll need to fix your bedroom’s humidity as well as replace the mattress.

Strong Musty Smell That Won’t Shift

Even after thorough cleaning, if the musty smell persists, mould remains in the internal layers. You can’t reach it with spray bottles.

That smell is mould spores releasing compounds into the air. You’re breathing those in all night. Time for a new mattress.

Already 8-10 Years Old

If your mattress was approaching replacement age anyway and has developed mould, take it as a sign. Don’t pour effort into saving something that was due for an upgrade.

A quality mattress should last 10-15 years with proper care. If you’ve got mould at year 8 or 9, invest in a new one.

Prevention Checklist: Stay Mould-Free

Weekly:

• Strip bed completely and air mattress for 30 minutes
• Check hygrometer reading (target 30-50%)

Monthly:

• Rotate or flip mattress (check manufacturer guidance)
• Vacuum mattress surface with upholstery attachment
• Check underside and edges for early warning signs

Seasonally:

• Deep clean mattress with upholstery cleaner
• Wash mattress protector (you do have one, right?)
• Check bed base slats for ventilation gaps

Annually:

• Consider professional mattress cleaning
• Assess whether base needs upgrading
• Replace pillows (they get mouldy too)

Mattress Mould FAQ

Q: What humidity level prevents mattress mould?
A: Maintain 30-50% humidity in your bedroom. Most UK bedrooms sit at 60-70% in winter, which encourages mould growth. Use a hygrometer to monitor levels and a dehumidifier to reduce excess moisture.

Q: How do I remove mould from a mattress UK?
A: For surface mould: 1) Vacuum both sides thoroughly, 2) Mix equal parts white vinegar and water, spray onto mould, leave 1 hour, 3) Scrub with stiff brush, 4) Blot dry completely, 5) Air in direct sunlight if possible. For stubborn mould, follow with baking soda overnight.

Q: When should I replace a mouldy mattress?
A: Replace immediately if: mould is larger than a dinner plate, you see black mould (Stachybotrys), mould appears on both sides, musty smell persists after cleaning, or the mattress is already 8-10 years old.

Q: Why does memory foam get mouldy?
A: Memory foam doesn’t breathe. It traps heat and moisture against your body. Over 8 hours, you release half a pint of perspiration with nowhere to go, creating perfect conditions for mould growth.

Q: Do natural fibre mattresses resist mould?
A: Yes. British wool contains lanolin, which naturally repels mould. Wool absorbs up to 30% of its weight in moisture without feeling damp, wicking it away from your body. Combined with breathable pocket springs, natural fibres prevent the conditions mould needs.

Summary

If you’re replacing a mould-damaged mattress, think about why it happened. Synthetic materials and poor airflow are usually the culprits. Reducing humidity, such as drying clothes outside of the bedroom (if possible) and opening a window each morning, will greatly reduce the potential of mould occurring. If really advanced mould is found on your mattress then the best option is to replace the mattress. Mould spores can really impact your breathing and exacerbate asthma and other respiratory problems.

Our Origins range uses natural fibres and pocket spring construction from £695 for a double. You get breathability, moisture-wicking, and that natural mould resistance we’ve been talking about.

The Artisan Naturals takes it further with 85% natural fibres including British wool, cotton, and horsehair. It’s two-sided, turnable, and built to last 12-15 years without mould issues because the materials themselves prevent the problem.

All our mattresses are made here in Yorkshire with natural materials because they solve problems like mould and overheating. Traditional materials work.

Questions about which mattress suits your situation? Ring us on 0161 437 4419 for honest advice. We’ll help you find the right solution, even if that’s not our most expensive option.