Rinse the stained area with cold water as soon as possible
Blot the stain with a clean cloth or paper towel
Apply a small amount of liquid laundry detergent directly to the stain
Gently rub the fabric against itself or use a soft brush
Let it sit for 10 to 15 minutes
Rinse again with cold water
Repeat if needed
For stubborn stains, soak the sheets in cold water with oxygen bleach
Wash the sheets in cold water
Check that the stain is gone before drying
Air-dry the sheets if any stain remains
Repeat the treatment if necessary