How to Remove Sweat Stains From Hats: 5 Easy, Safe Steps

A paste of baking soda and water, a soft toothbrush and a cool rinse take most sweat stains off a cotton or polyester baseball cap. Before you learn how to remove sweat stains from hats, check two things, because the brim and the dye decide which method is safe. Old caps can hide a cardboard brim that falls apart in water, and some fabrics bleed color the moment they get wet. Below is how to remove sweat stains from hats of every common type, from gym caps to wool beanies and straw sun hats.

Check the Brim and the Dye First

Tap or flick the brim with a fingernail and listen to the sound it makes. Maytag explains that a hollow sound usually means a cardboard bill, which many caps made before 1983 still have. A cardboard brim warps and softens in water, so that hat can only be spot cleaned.

Next, test the dye on a hidden spot inside the hat. Dampen a white cloth with water and a drop of detergent, then press it against the inner band for a minute. Family Handyman warns that if dye comes off, the hat should not be washed in water at all. Skipping this test is the most common mistake in how to remove sweat stains from hats, and it can leave a faded patch that no cleaner will fix.

How to Remove Sweat Stains From Hats With Baking Soda

This paste method is the safest choice for how to remove sweat stains from hats made of cotton, twill or polyester with a plastic brim.

Mix three tablespoons of baking soda with one tablespoon of water to make a thick paste.
Spread it over the yellow band and the underside of the brim where sweat collects.
Add a few drops of white vinegar and let it fizz for a minute.
Scrub gently with a soft toothbrush in small circles, working with the fabric weave.
Leave it for about 30 minutes, then rinse with cool water until the paste is gone.

For darker yellow lines, Maytag uses a stronger paste of half a cup of baking soda, one tablespoon of salt and one tablespoon of hydrogen peroxide. Peroxide can lighten colors, so save that mix for white or light caps and test it first.

Hand Washing a Sweaty Baseball Cap

A full hand wash is the next step in how to remove sweat stains from hats when the whole crown smells or looks dingy. Fill a sink with cool water and a little mild detergent, such as Woolite or a drop of dish soap. Pre-treat the band with a stain spray like OxiClean, then let the cap soak for about 30 minutes.

Nike suggests rubbing a little shampoo into stubborn sweat lines on the inner band, since shampoo is made to break up body oils. Scrub the band with a toothbrush, rinse with cool water, and press out the water with a towel instead of wringing. This full soak is how to remove sweat stains from hats that have been worn all summer without a wash.

Cardboard Brims, Wool and Straw Hats

Vintage caps with cardboard brims need spot cleaning only, which changes how to remove sweat stains from hats of that age. Dip a clean cloth in cool water with a drop of mild detergent, wring it until it is barely damp, and dab the band. Keep the cloth away from the brim, then blot the band dry with a towel straight away.

Wool caps and beanies shrink and felt in hot water, so use a wool detergent and cool water only. Nike recommends diluting a mild wool wash in water and scrubbing gently, since wool loses its shape easily. Straw hats and felt fedoras should never be soaked, so wipe the sweatband with a damp cloth and a little gentle soap, then let it air dry. A dedicated hat shop or dry cleaner is the better choice for an expensive felt hat.

Drying a Hat So It Keeps Its Shape

Drying is the step people rush when they learn how to remove sweat stains from hats, yet a wet cap collapses into an odd shape if you leave it flat. Set the cap over an upside-down bowl, a coffee can or a rolled towel that mimics the curve of your head.

Keep it out of direct sunlight, which can fade colors, and never put a cap in the dryer. Molly Maid also advises avoiding any product with bleach, since it can leave pale spots on colored fabric. Let the cap dry fully, usually overnight, before you wear it again or the band will start collecting sweat right away.

How to Stop Sweat Stains Coming Back

Prevention is easier than repeating how to remove sweat stains from hats every few weeks. Wash a gym cap after every few wears instead of waiting for the yellow line to appear. Disposable or washable hat liners stick inside the sweatband and catch most of the sweat before it reaches the fabric.

Wipe the band with a damp cloth after a hot day, and let the cap air out instead of tossing it in a bag. If you sweat heavily, a fresh antiperspirant on the hairline can also help, though it may leave its own residue. Our guide on how to remove deodorant stains covers that problem, and more fabric fixes are in our laundry and stains guides.

Related guides:

FAQs

Can I put a baseball cap in the washing machine?

You can wash a modern cap with a plastic brim on a gentle cold cycle inside a mesh bag, if the label allows it. Skip the machine for any cap with a cardboard brim, wool fabric or delicate embroidery.

Does the dishwasher really clean hats?

Some people use the top rack of a dishwasher without detergent pods, but heat and harsh detergent can warp the brim and fade the color. Hand washing gives you far more control and is safer for caps you care about.

Why does my white hat turn yellow?

Sweat contains oils and proteins that react with antiperspirant and the air, which slowly turns the band yellow. Learning how to remove sweat stains from hats early stops that color from setting deeper into the fibers. The baking soda and peroxide paste works best on white caps after a patch test.

Can I use bleach on a sweat-stained hat?

Chlorine bleach can react with sweat proteins and make yellow stains darker, and it weakens fibers. Use an oxygen cleaner such as OxiClean instead, and only on colorfast fabric.

Final Thoughts

Check the brim, test the dye, and start with baking soda before reaching for anything stronger. Once you know how to remove sweat stains from hats, a quick clean every few weeks keeps your favorite cap looking new for years.