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Why Does My Laundry Still Smell Bad After I Wash It?

Some would argue that there are few household chores worse than laundry—the tedious rinse-and-repeat cycle that sprawls over our domestic calendars. After all, there’s a reason it’s called “laundry day,” not “laundry hour.”

 

And here’s what makes it worse: Devoting a whole day or night to washing a mountain of clothing, only to have it come out still smelling a little funky.

 

You know what we’re talking about. Lingering bad odors on should-be-clean laundry is something nearly half of all people experience, according to consumer goods company Procter & Gamble.

 

And unfortunately, there are lots of gross reasons for that. We asked some scientists to break it down for us—and trust us, you’ll be running to your washing machine after you finish reading this.

 

Body soils that don’t wash out

Let’s start by taking a look at what makes dirty laundry, well, dirty. It might come as no surprise, but 70% of laundry dirt is caused by body soils, which are often invisible to the human eye.

 

On a normal day, even without working out, the average adult produces 1 liter of sweat, 40 grams of sebum (the same body oil that, in large quantities, is responsible for acne), 10 grams of skin cells (that’s about 2 billion cells per day), and 10 grams of salt, explains Mary Begovic Johnson, Tide and Downy principal scientist at Procter & Gamble Fabric Care.

 

All of this stuff, of course, gets transferred to your clothes, towels, and sheets. And if your laundry detergent doesn’t effectively get rid of it, all that gunk will continue to accumulate around—and even within—the fibers of your favorite jeans, bath towels, pillowcases, and so on.

 

The most challenging to get rid of could be acne-causing sebum.

 

“Sebum is a hard fat with a high melting point that makes it very sticky and hard to remove from clothes as it sets in over time,” Johnson explains. “Sebum’s stickiness also attracts other odor-causing soils to fabrics.”

 

If you don’t successfully wash away sebum or other body soils out of your clothes, “over time, they’ll break down to form volatile—or easy to get into the air—malodorous compounds,” Johnson says.

 

These compounds are directly related to the ones responsible for the foul odors of stinky cheese (isovaleric acid), rotting meat (cadaverine), and vomit (butyric acid), she says.

 

Too much moisture

“Biology is at the root of most, if not all, off-odors in a household context,” says Bill Carroll, adjunct professor of chemistry at Indiana University in Bloomington.

 

Just like your old house can get a musty smell after lots of rain, moisture can also be the culprit behind fusty-smelling clothes. We call it mold or mildew. Either way, fungus spores are to blame.

 

“Fungus spores are in the air around us, all the time,” Carroll notes. “They love a moist environment, and laundry that’s been left damp for too long falls into that category—even if that dampness is just high humidity.”

 

Fungi also love the dark, Carroll adds, which means drying your laundry in your basement is just asking for stinky socks.

 

Pollutants

Recently, a reporter for the New York Times sent Johnson’s team a random bundle of vintage clothing to be tested for odors.

 

Of the 18 odors detected, 12 were derived from body soils, Johnson says.

 

“The source of the remaining compounds included environmental contaminants like car exhaust, gasoline, dry-cleaning solvents, food, and perfume,” she explains.

 

Over time, the molecules of all of these things break down in your clothes to produce that distinctive (and hard to get rid of) “off” smell—which explains the distinctive odor of vintage-clothing stores.

 

Your washer

As Alanis Morissette would say, “Isn’t it ironic?” Sometimes your washing machine is to blame for icky-smelling clothes.

 

“Some combination of body odor, oil, and other disgusting detritus can be absorbed into [your machine’s] gaskets or trapped in seams and crevices,” Carroll explains. “Additionally, gooey fabric softener that doesn’t fully rinse out and stays around for a long time can also act as food for the fungi.”

 

How to combat bad laundry odors

Despite all of this, you’re not doomed to walk around, surreptitiously sniffing your collar and worrying, “Is that smell coming from me?” for the rest of eternity. Here’s what will help.

 

Wash with hot water, if you can: Washing in hot water melts that aforementioned nasty sebum, making it easier to remove from your clothes. Yet 43% of consumers in North America wash all or most of their laundry loads in cold water, Johnson says. Warmer always washes better—but check the labels of your clothes to make sure they can take it.

 

Be choosy about your detergent: Look for an ingredient called polymers, which capture soils in the water and prevent them from redepositing back onto your clothes.

 

“This is especially important in high-efficiency washers as they use very little water for very large loads—leading to very soiled wash water,” Johnson says.

 

Don’t be swayed by fancy fragrances: Just because your detergent smells like a rainy summer day or field of lilacs doesn’t mean it’s truly getting your clothes clean.

 

“Heavy perfumes in these detergents mask the odors, but as the perfumes fade, the odors become noticeable again,” Johnson says.

 

Dry your laundry completely: If you leave clothes or towels sitting around in unlit areas (aka your gym bag) while they’re still damp, “within six to 12 hours you will have growth of mold and mildew,” Johnson warns.

Allow your clothes or towels to air-dry before placing them in the hamper. And since odors transfer between clothes, consider a separate laundry basket for sweaty workout gear.

 

Clean your washer: “Disinfection is the answer for rogue biology,” Carroll says. “Sometimes you have to wash the washer.”

 

Run your washer through a cycle with a 50-50 mix of water and white vinegar. (Check your owner’s manual first.) Then, take a sponge and clean in and around all the nooks and crannies—like your soap dispenser—where bacteria can grow.

 

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