How to Get Sweat Stains out of Shirts

Sweat stains can ruin the look and feel of your shirts, leaving the underarms stiff from product build-up and soiled with ugly yellow stains. You may think that sweat stains only really happen to white or light-colored shirts, but these compound stains can happen to shirts of any color or material.

When it comes to removing sweat stains from shirts, it's important to understand the complicated science behind what causes them—it's not just sweat, believe it or not!—in order to effectively break them down and restore shirts to an almost-brand new state.

What Causes Sweat Stains

The term sweat stains is a bit of a misnomer: Sweat stains are actually complicated combination stains that are made up of organic and inorganic compounds.

What we think of as sweat stains—the yellowish staining and waxy, cardboard-like buildup on the underarms of shirts—are caused by sweat, but also by the ingredients in the antiperspirants we use to prevent sweat.

Most antiperspirants contain aluminum, and that aluminum can cause those deep stains and stiffness in shirt fabric. (One way to prevent these types of stains is to switch to a deodorant that does not include aluminum in its formula.)

But even if you do start using an aluminum-free deodorant or anti-perspirant, the chemistry of these tricky stains doesn't stop there: There is sweat itself, as well as dead skin and sebum that transfers from the body to clothing, which are protein stains; deodorants also contain wax- and/or petrochemical-based ingredients, which help to contribute to the buildup we associate with sweat stains.

Treating Fresh vs. Set-in Sweat Stains

To further complicate matters, sweat stains come in two forms—fresh or set-in—and treating them requires different methods. Note: These instructions are for machine- or hand-washable fabrics such as cotton, denim, linen, nylon, polyester, and spandex; if the care tag says that fabric content includes rayon, silk, triacetate, or wool, the shirt will typically need to be dry cleaned.

Fresh sweat stains, which will appear as light yellow patches that stain the underarm of shirts, should be pretreated with an enzymatic formula like Krud Kutter Sports Stain Remover or Zout prior to laundering. It can also help to include a laundry booster, an in-wash product that is used in conjunction with and in addition to laundry detergent, such as Borax or an oxygenated bleach like OxiClean. Using one of those products as part of a regular laundry routine will help to keep shirts from developing set-in sweat stains.

Set-in sweat stains require a more intensive stain removal process, although most of it is hands-off and won't require a tremendous effort. To eliminate set-in sweat stains, it's best to soak shirts in a solution of oxygen bleach, laundry detergent, and water for an hour up to overnight; extended exposure in the form of soaking will help to break down the waxy buildup and deep staining.

During soaking, using a laundry brush to move the stain-removing solution into the fibers will also help to break down these tough compound stains. Laundry brushes allow you to work stain treatments into fabric and, in the case of sweat stains, will also help to break down the product buildup that creates that stiff, cardboard-y feeling.

How to Remove Fresh Sweat Stains

To eliminate fresh sweat stains from the underarms of shirts, pretreat stains prior to laundering using an enzymatic stain remover. If sweat stains are a regular problem, you can leave the stain remover next to your laundry hamper—that way, you can easily grab the bottle, spritz the stains, and toss the shirt in the laundry bin.

What You'll Need

• An enzymatic stain remover like Krud Kutter Sports Stain Remover or Zout
• Laundry detergent
• A laundry booster like Borax or OxiClean (optional)

Step 1: Apply Stain Treatment Products

Use an enzymatic stain removal formula like Krud Kutter Sports Stain Remover or Zout to pre-treat sweat stains on shirts prior to laundering. After applying the stain treatment to the shirt, it can help to rub the fabric against itself. This optional step will help to force the stain remover into the fibers.

Step 2: Launder as Usual

Launder the pretreated shirts as usual, and consider adding a laundry booster like Borax or OxiClean to the wash to provide another level of stain elimination.

How to Remove Set-in Sweat Stains

To eliminate set-in sweat stains from the underarms of shirts, soak them in a stain-removing solution for an hour up to overnight prior to laundering.

What You'll Need

• Oxygen bleach
• Liquid or powder laundry detergent
• A laundry brush (optional, but strongly recommended)
• A wash basin (optional)

Step 1: Prepare an Oxygen Bleach Solution

Start by finding a clean space, like the kitchen sink, a utility sink, a washing bucket, etc., that's big enough to fully submerge the shirt, or shirts, in water and sit undisturbed for an hour up to overnight.

Make a stain removing solution by dissolving oxygen bleach in hot water according to package directions. Add a tablespoon of liquid or powder laundry detergent to the solution; do not use laundry pods or packs when making a soaking solution, as puncturing a detergent pod is a safety hazard.

Step 2: Submerge and Soak the Shirt

Submerge the shirt and allow it to soak for at least an hour up to overnight. Periodically agitate the shirt, either by using your hands to rub the stained part of the fabric against itself while the shirt is submerged or by using a laundry brush to push the stain solution deeper into the fibers of the shirt, which will also help to lift off waxy product build-up from deodorant.

Step 3: Drain the Solution and Launder the Shirt

Drain the soaking solution and squeeze excess water out of the shirt, then launder it as usual.