How to Remove Yellow Stains in Shirt Underarms

Yellow stains in the underarms of white shirts are not caused by sweat alone. Antiperspirant residue, body oils and salts in perspiration can build up in the fibres, creating a crust that is difficult to remove, particularly if the garment has repeatedly been washed and tumble-dried without pre-treatment.

Why do sweat and antiperspirant turn a shirt yellow?

Many antiperspirants contain aluminium-based compounds that temporarily reduce the amount of sweat reaching the skin. On clothing, these ingredients can combine with perspiration, body residue and other components in the product, forming deposits that tend to become trapped around the underarms.

As this material builds up, the affected area may become stiffer and more yellow. A standard wash does not always fully dissolve the crust, which is why old stains often need pre-treatment and more than one attempt before they disappear.

• Sweat and body salts can remain trapped in the fibres;
• Antiperspirant residue may create a hardened layer;
• Skin oils also contribute to the build-up;
• Tumble-dryer heat can make stubborn stains harder to remove;
• The older the mark, the more labour-intensive the treatment is likely to be.

How should you use bicarbonate of soda and hydrogen peroxide on the stain?

For white shirts that are suitable for these products, a blend of bicarbonate of soda, water and 3% hydrogen peroxide can be applied to the yellowed area and left for a few minutes before washing. First test it on a concealed area, follow the care label and rinse thoroughly before putting the shirt in the washing machine. Similar mixtures are used to pre-treat deodorant deposits on white fabrics.

What is the step-by-step method for treating an old stain?

Turn the shirt inside out so that you can treat the section that was in direct contact with the skin. Spread a small amount of the paste over the stain without soaking the whole garment, leave it for around 30 minutes, then gently rub with your fingers or a soft brush before washing.

Next, wash the shirt at the highest temperature allowed by its care label, then air-dry it so you can check the result before using a tumble dryer. If yellowing remains, the treatment may need repeating. Other methods for restoring yellowed white clothing also depend on checking the fabric composition first.

• Check the care label before beginning treatment;
• Test the mixture on an inconspicuous area;
• Apply it only to the yellowed section;
• Leave it to work for approximately 30 minutes;
• Rub gently, without wearing down the fibres;
• Wash as usual and inspect the stain before drying with heat.

Should chlorine bleach be avoided?

Chlorine bleach should not be considered forbidden for every white shirt: some cotton and polyester fabrics permit it when the care label approves its use. However, it must not be mixed with hydrogen peroxide or other products, while garments containing elastane, wool, silk or particular finishes may require non-chlorine bleach. For persistent sweat stains, enzyme-based products or oxygen-based bleaches are also suitable alternatives.

How can you stop yellowing returning to shirt underarms?

Allowing antiperspirant to dry before putting on a shirt reduces the amount of product transferred directly to the fabric. An undershirt also provides a barrier against sweat and residue, while washing sweaty clothing-or at least allowing it to dry in a well-ventilated place-prevents it from remaining damp and piled up for several days.

Prevention works best when build-up is removed before it forms a thick crust. Washing shirts after heavy wear, avoiding excessive amounts of antiperspirant and checking the underarms before drying help prevent successive layers of sweat and product from turning a faint mark into a permanent yellow stain.