* Sweat and Body Oils: Sweat and oils from your body can react with the fabric, causing discoloration.
* Detergent and Water: Harsh detergents and hard water can also contribute to yellowing.
* Exposure to Sunlight: Sunlight can bleach the white fabric, making it appear yellowish.
* Age and Wear: Over time, the fabric simply ages and can become discolored.
The yellowing isn't necessarily a sign of dirt, but rather a combination of the factors above.
To prevent yellowing, you can:
* Wash them regularly: This helps remove sweat and oils before they have a chance to set in.
* Use a gentle detergent: Avoid harsh detergents that can damage the fabric.
* Use soft water: If you have hard water, consider using a water softener.
* Avoid excessive sunlight exposure: Hang your boxers to dry in a shaded area.
Even with these measures, some yellowing is inevitable, and it's often considered a sign that the boxers are worn-in and comfortable!