How to remove mildew smell from towels (sour or musty)

Step by step

1. 1

   Wash hot, in a smaller load

   Wash smelly towels in hot water (120 to 140°F) with heavy-duty detergent, using the full recommended amount. Don't overfill the drum.

   Why: Hot water and enough detergent remove the skin oil and soil the bacteria feed on, and reach growth deep in thick cotton.

2. 2

   Add bleach the towels can take

   For white or bleach-safe towels, add chlorine bleach to the wash. For colored towels, soak them in oxygen bleach and hot water for at least 30 minutes first, then wash.

   Why: Bleach oxidizes mold and the odor-producing bacteria that a plain wash can leave behind.

3. 3

   Dry them completely, straight away

   Move towels to the dryer or a line the moment the cycle ends, and dry them all the way through. Thick hems and folded edges dry last.

   Why: The sour compound is made while towels stay damp. Fast, full drying stops growth before it starts again.

4. 4

   Smell-check and repeat if needed

   Smell the towels once dry. If a sour or musty note is still there, wash hot again, or soak in baking soda and water and rewash.

   Why: Heavily affected towels can need more than one round.

5. 5

   Hang towels to dry between uses

   After each use, spread towels flat on a bar or hook where air moves. Don't leave them in a heap, on the floor or in the hamper while damp.

   Why: A bunched-up damp towel in a humid bathroom is where mildew and odor bacteria grow fastest.

Why towels smell sour even after washing

Towels are thick, absorbent cotton that stays damp for a long time, usually in a humid bathroom. They pick up skin oil, skin cells and soil every use, which feed bacteria. In a study of smelly household laundry, mostly towels, researchers found the bacterium Moraxella osloensis at high frequency. It makes 4-methyl-3-hexenoic acid, described as a wet, dirty dishcloth smell, and it survives washing, drying and UV light.

That's why towels can come out of the wash smelling fine and turn sour after one use: the surviving bacteria wake up as soon as the towel gets wet again. Mildew, the musty-smelling mold, grows on towels left damp as well. See the mildew smell page for the wider picture.

Why hot water, bleach and drying fix it

Hot water and enough detergent strip the oils and soil the microbes live on. Bleach oxidizes the mold and bacteria that remain. Drying fast and completely removes the moisture they need to regrow.

Sun-drying alone isn't a reliable fix, because these bacteria tolerate drying and UV. Wash first, then dry. For more on everyday towel care, see smelly towels and water temperature.

By situation

Towels smell sour after one use

Bacteria survived the wash. Do a hot wash with bleach the towels can take, dry them completely, and hang them spread out between uses.

Musty towels from the linen closet

They were put away before they were fully dry, or the closet is damp. Rewash hot, dry thoroughly before folding, and keep the closet aired.

Colored towels

Use oxygen bleach rather than chlorine, which can fade the color. Soak at least 30 minutes, then wash hot.

Kitchen towels

Kitchen towels, especially any that ended up being used in the bathroom, should be washed hot, or warm with bleach.

Everything from the washer smells musty

The washer itself may be the source. Clean it and leave the door open between loads. See mildew smell in a washing machine.

What not to do

• Don't leave wet towels in the washer, a pile or the hamper. Mildew and odor bacteria grow quickly on damp textiles.
• Don't cover the smell with fabric softener or scent boosters. They add fragrance on top of the bacteria, and the sour smell returns when the towel gets wet.
• Don't rely on sun-drying alone. The main sour-smell bacteria tolerate drying and UV light.
• Don't mix chlorine bleach with vinegar or ammonia. The combinations release toxic gases.

Other methods that work

Baking soda soak

For a lingering smell, soak the towels in baking soda dissolved in water, then wash again.

Caution: It's a supplement to a hot wash, not a replacement.

Chlorine bleach spot soak

For white towels with mildew spots, soak in 2 tablespoons of liquid chlorine bleach per quart of water for 5 to 15 minutes, then rinse and wash.

Caution: Test colored towels first, and ventilate when using bleach.

Stain still there?

Towels smell fine dry but sour when wet

Bacteria are still in the fibers. Wash hot with bleach the towels can take, and make sure they dry fully each time.

Towels have black or gray specks

That's mildew growth. Treat with bleach as the fabric allows; old mildew stains may not come out completely.

Safety

• Ventilate when using chlorine bleach, and never combine it with ammonia or acids.

Never mix cleaning products; see chemicals you must never combine.

Questions

Mildew elsewhere

• Mildew: what causes it and how to remove it
• Mildew in a basement
• Mildew in a car
• Mildew in carpet
• Mildew in clothes
• Mildew in the house
• Mildew in a washing machine