First, try to prevent stains in the first place.
When applying your antiperspirant, apply just a thin layer of the product (experts say that one swipe up and one swipe down is plenty) and gently massage it into your skin. Allow the antiperspirant to dry before putting on your shirt. Or, better yet, apply your antiperspirant at night before bedtime. Bedtime application has been shown to be more effective than morning application and you'll avoid getting the product on your clothing. And, yes, you can still shower. Antiperspirants work by plugging your sweat ducts and the plugs can withstand routine showering.
During the day, use undershirts or dress/shirt shields to help prevent perspiration and antiperspirant products from soaking directly into fabrics.
Rinse the sweaty areas of your clothing with cold water as soon as possible after you remove the garments. The longer substances stay on fabrics, the greater damage or the more permanent the stain or discoloration.
If you take your clothing to a dry cleaner, ask to have the underarms and other affected areas pre-treated for perspiration.
If, despite your best efforts, you still find stains on the underarms of your clothes, you can salvage the situation. Turn your garment inside out, rinse the affected area with cold water and pre-treat it (see below for pre-treatment options). Let the garment sit for 30 minutes.
To pre-treat yellow stains, dab the area with detergent, ammonia, white vinegar, a bleach stick, or hydrogen peroxide. You may also want to try soaking the clothing in water with an enzyme-containing laundry product. Enzyme laundry aids help to remove organic stains such as sweat.
To pre-treat stains that include color changes or "bleaching" of fabrics, apply ammonia to a fresh stain or white vinegar to an old stain, then rinse. Ammonia is alkaline and helps to neutralize acidic substances such as fresh antiperspirant and sweat. Old stains have, however, already oxidized which is why ammonia is no longer recommended but white vinegar might be effective. Warning! Do not mix ammonia or ammonia-containing preparations with chlorine bleach or substances containing chlorine bleach. This will produce hazardous fumes.
After your pretreatment regime, wash your clothing in the hottest water that the fabric will tolerate with detergent containing color-safe bleach. If stains remain after washing, treat them again and rewash. Don't put the clothing in the dryer until you've removed the stain or given up – the heat of the dryer will set the stain and make it even harder, if not impossible, to remove.
The tips provided here come, in part, from Cheryl Mendelson's book Laundry, The Home Comforts Book of Caring for Clothes and Linens (Schribner, 2005) and the makers of Tide laundry detergent (Procter & Gamble). They were first compiled for hyperhidrosis sufferers in our newsletter SweatSolutions, subscribe today!