Proven Way: How To Get Mildew Out Of Comforter (2026)

By Sarah Mitchell · December 19, 2025

Immediate Action (first 5 minutes)

The second you pull that musty comforter out of storage, stop. Don't just throw it on your bed. Mildew spores spread incredibly fast. If you shake it indoors, you're just dusting your bedroom with fungal spores.

Grab the comforter and take it outside immediately. I always keep a stiff-bristled brush by my back door for this exact reason. Lay the comforter flat on a clean patio table or hang it over a railing. Brush the visible black or green spots vigorously. You want to knock off as many surface spores as possible before they embed deeper into the batting.

Next, isolate it. Don't toss it in your indoor laundry hamper. Put it in a plastic garbage bag until you're ready to wash it. This keeps the spores from jumping onto your clean clothes. If the smell is making your eyes water, spray the spots lightly with plain white vinegar from a spray bottle. This halts the spore growth instantly while you prep your washing machine.

What You'll Need (tools/products)

I've ruined a few expensive down comforters over the years by using the wrong chemicals. Chlorine bleach will destroy the fibers and leave yellow stains. You need specific, fabric-safe tools to kill the fungus without melting the synthetic fill or stripping natural down oils.

Item	Brand Recommendation	Estimated Cost
Oxygen Bleach	OxiClean Versatile Stain Remover	$12 - $15
Heavy Duty Detergent	Tide Hygienic Clean Heavy Duty	$10 - $14
White Vinegar	Heinz Distilled White (1 Gallon)	$4 - $6
Stiff Brush	Rubbermaid Reveal Scrub Brush	$5 - $8
Enzyme Cleaner (Backup)	Nature's Miracle Stain & Odor	$12 - $18

You'll also need access to a large-capacity washer. If your home washer is under 4.5 cubic feet, it won't agitate a thick king-size comforter properly. Spend the $6 to use the giant commercial front-loaders at your local laundromat. It's worth the trip.

Step-by-Step Removal

This is the exact method I use when clients bring me bedding that's been sitting in a damp basement. It takes a few hours, but it saves you from buying a $200 replacement.

Step 1: Pre-treat the visible spots

Mix equal parts distilled white vinegar and cool water in a spray bottle. Spray the mildew stains until they are saturated. Let this sit for exactly 15 minutes. The acetic acid in the vinegar breaks down the fungal cell walls. Don't let it dry out. If it starts to dry, mist it again.

Step 2: Load the washer correctly

Stuff the comforter into the drum loosely. It needs room to tumble. If you have to force the door shut, the machine is too small. Add your heavy-duty detergent to the dispenser. I use about 2 tablespoons of Tide Hygienic Clean. Next, scoop half a cup of OxiClean powder directly into the drum. Don't use liquid bleach.

Step 3: Select the right temperature and cycle

Set the water temperature to warm, around 90°F to 100°F. Hot water can shrink the cotton shell or melt synthetic microfiber fills. Choose the "Bulky" or "Bedding" cycle. This cycle uses more water and a slower spin speed, which prevents the fill from clumping into a giant ball in one corner. Let it run the full 90-minute cycle.

Step 4: The white vinegar rinse

Once the wash cycle finishes, run a second rinse cycle. Pour 1 cup of plain white vinegar into the fabric softener dispenser. This strips away any leftover detergent residue. Detergent buildup actually feeds mildew, so getting it all out is critical. It also naturally softens the fabric.

Step 5: Dry completely with tennis balls

This is where most people fail. A damp comforter will grow mildew again in 24 hours. Toss the comforter into a large dryer with three clean wool dryer balls or clean tennis balls. The balls beat the filling, keeping it fluffy. Dry on medium heat (around 130°F) for at least 90 minutes. Check it every 30 minutes. Break apart any clumps of fill you feel with your hands. It must be 100% bone dry before you put it back on the bed.

Alternative Methods

Sometimes the vinegar and oxygen bleach combo doesn't cut it. If you're dealing with a delicate down comforter or a stubborn black mold stain, try these backups.

Borax Soak for Heavy Odors

If the musty smell lingers after washing, Borax is your best friend. Fill a bathtub with 4 inches of warm water. Dissolve 1/2 cup of 20 Mule Team Borax into the water. Submerge the comforter and stomp on it with clean feet to push the water through the fibers. Let it soak for 45 minutes. Drain the tub, then transfer the comforter to the washer for a quick rinse cycle. Borax raises the water's pH, creating an environment where fungus simply can't survive.

Enzyme Cleaners for Organic Stains

If the mildew is mixed with body oils or pet dander, oxygen bleach might struggle. I've had great luck using Nature's Miracle Laundry Boost. The enzymes literally eat the organic proteins that the mildew is feeding on. Add 1/4 cup to your detergent dispenser and wash on a cold, delicate cycle. This is especially safe for expensive goose down comforters that can't handle warm water.

Commercial Laundromat Ozone Wash

I'll be honest, this takes elbow grease and a car trip. Some modern laundromats have commercial washers with built-in ozone (O3) cleaning cycles. Ozone gas injected into the water oxidizes and destroys mold spores at a molecular level without using hot water. It usually costs about $8 per load. If your comforter is a dry-clean-only silk blend, this is the safest route before resorting to a professional cleaner.

Prevention Tips

Getting the mildew out is only half the battle. You have to stop it from coming back. I see this issue constantly with people who live in humid climates or store bedding improperly.

Ditch the plastic bins: Never store comforters in sealed plastic tubs. Plastic traps ambient moisture. Use breathable cotton canvas storage bags instead. They let air circulate while keeping dust out.
Use silica gel packs: Throw 4 or 5 large silica gel desiccant packets into your bedding storage bags. You can buy a 10-pack of Dry & 20g packets on Amazon for about $12. They absorb excess humidity during the summer months.
Wash before storing: Even if it looks clean, wash the comforter before putting it away for the season. Dead skin cells and invisible sweat stains are a buffet for mildew spores.
Control bedroom humidity: Keep your bedroom humidity below 50%. If you don't have central AC, run a 35-pint dehumidifier like the Vellgoo DryJack in the corner of your room during humid months.
Air it out: If you use a duvet cover, strip it off once a month and hang the bare comforter outside in direct sunlight for 2 hours. UV rays naturally kill surface spores.

FAQ

Can I use chlorine bleach to kill the mildew?

I strongly advise against using chlorine bleach on comforters. It will weaken the cotton or polyester shell and cause the fabric to tear over time. It also leaves a harsh chemical smell that is nearly impossible to rinse out of thick batting. Stick to oxygen bleach or white vinegar for safe, effective results.

Will the mildew smell go away completely?

Yes, but it might take two wash cycles to fully neutralize the odor. The musty smell is caused by microbial volatile organic compounds (mVOCs) that get trapped in the thick filling. The white vinegar rinse step is crucial because it breaks down these compounds rather than just masking them with floral perfume.

Is it safe to sleep with a comforter that had mildew?

Only if you have successfully washed and completely dried it. Sleeping under a comforter with active mildew can trigger severe allergic reactions, asthma attacks, and respiratory irritation. If you still see dark spots or smell a damp, earthy odor after washing, do not use it. Run it through the Borax soak method or take it to a professional textile cleaner.

How do I know if my comforter is too far gone to save?

If the fabric shell feels brittle, tears easily when you pull it, or if the mildew has rotted through the stitching, it's time to throw it away. I've seen comforters where the inner down fill has turned into a solid, foul-smelling brick. No amount of washing will fix structural rot or deeply embedded fungal decay in the core filling.