How to whiten white clothes and remove old yellowish stains

Using aspirin
To remove yellowish stains from under the armpits you can apply the aspirin method. It is a very simple trick, which consists of putting one or two aspirin tablets in the washing machine drum.

The fizz of the aspirin will help remove sweat stains.

Cold water and hydrogen peroxide
Another effective method for removing yellowish stains from white clothes is to soak them in a solution of cold water and hydrogen peroxide.

After a couple of hours you can wash the garment normally. If the stain does not come out, you can use hydrogen peroxide directly, without mixing it with water.