Knit shirts are a wardrobe staple. Cool and comfortable, they don't easily wrinkle and they come in a variety of colors. Most knit fabrics don't need special care, and they can be cleaned in a washing machine with regular detergent, and put in a clothes dryer. However, the synthetic fibers of some knits make removing stains more difficult, while some shirts can't be treated with harsh stain removers, which might affect a shirt's bright colors. Different stains require different approaches, and you may need to try several methods before you find one that successfully removes the stain.
Blot wet stains with a dry, absorbent cloth. If a stain has already dried, brush the spot with a clothes brush to remove as much of the dried matter as possible. As you do this, try to determine what caused the stain.
Consult the garment's care label. If the label says "Dry Clean Only," take the shirt to a professional cleaner and point out the stain. Give them as much information as you know about the source of the stain and ask them to remove it for you.
Soak washable garments in cold water for 30 minutes, which could be enough to remove light stains. If the stain remains after half an hour, work a little shampoo, liquid dish detergent or liquid laundry detergent into the stain with your fingers and soak for another half an hour. Soak stubborn stains overnight in laundry detergent and water, or in laundry pre-soak powder diluted with water.
Wash the shirt in the water temperature recommended on the label, which will usually range from cool to warm (knit shirts could shrink or fade in hot water).
Treat stains with a commercial stain treatment product. Apply the product to the shirt and launder the garment once more.
Take washable shirts with stubborn stains to the dry cleaner if self-cleaning does not work.