Avoid putting your shirt on for around 30 seconds after you have applied deodorant; this will give your deodorant time to dry and should reduce the chances of a stain occurring.
As soon as you can soak the garment for an hour in warm water.
Wash as usual, (check washing instructions) adding 60mls of Vanish gel to your normal detergent.
Underarm sweat stains occur when anti-perspirant ingredients mix with the natural salts in sweat. Many deodorants contain aluminium compounds to reduce moisture. This aluminium is behind the stain build-up and yellowing of fabrics. You're most likely to find these stains occur after continuous wear rather than suddenly appearing.
Sweat stains... The harder you work the more likely they become! It's often difficult to work out if the sweat stain has been caused by perspiration, or if the stain is a result of the deodorant you've been using. Vanish Oxi Action can deal with both and this means you don’t have to worry about sweat stains again.