Take a toothbrush and scrub the sweaty parts of the hat with some shampoo, then wash the hat. most hats will keep their shape just fine in the washer and dryer.....or air dry. shampoo is made to break down body oils. you can also use this tip for ring-around-the-collar.
You can also stop sweat stains before they happen. I use a product called Hat Saver that you spray on the outside of your new hat and you never get sweat stains to clean. I then just wash the headband on the inside of the hat if it starts to smell or gets real dirty. You can buy it at hatsaver.com.
In addition to sprays and washing, you can also protect your hat with a wicking hat liner, like the CrownWear Head Liner. The keep sweat out of your eyes and filter out the dirt, salt and oils in your sweat to prevent stains and odors and extend the life of your hat.
You get rid of oil stains by using oxce clean
your mom
peroxyed
I do believe perspiration (a.k.a. sweat) is caused because the body is trying to get rid of the toxic gases and other bad things inside the body. I do hope this helps.
Rub it clean with arsenic
An application of a good quality talcum powder will help absorb sweat.
Try Resolve carpet cleaner, that worked to get most all of the stains out of my carpet when i moved.
Try a little bit of Golden Syrup (see 'How do you remove grass stains?)
Perspiration is salty because it contains electrolytes such as sodium and chloride that are present in the body fluids. These electrolytes are released through sweat glands to help regulate the body's temperature and maintain the balance of fluids in the body.
use Angel Eyes. http://www.angelseyesonline.com/ amazing product. it really works. they got rid of my Bichon Frise's tear stains. you should try it out.
Any good toilet cleaner will remove the stains.
By spilling spaghetti sauce on your shirt! Or bleach. Or shout.