Mayonnaise is an oil-based stain and should be pretreated using a solvent-based stain removal product, like Shout or Spray 'n Wash. If you don't have a solvent-based pretreater, apply heavy-duty liquid detergent to the stain and work it in by gently rubbing.
After pretreatment, wash the garment as usual in the hottest water appropriate for the fabric using the recommended amount of detergent for a regular load. Inspect the garment before drying and repeat treatment if necessary.
If the garment is dry clean only, point out and identify the stain to your professional cleaner. If you are using a home dry cleaning kit, be sure to treat the stain with the provided stain remover before putting the garment in the dryer bag.
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