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Take an old toothbrush and use the bristles to thoroughly scrub at the mold on your item of clothing. Remove as much of the mold buildup as you can this way. Discard the toothbrush immediately after scrubbing the fabric.  Work in a well-ventilated area, or even outdoors. Mold spores can travel through the air in your house and could settle onto other clothing, or worse, in your lungs. Once you’ve scrubbed off as much of the mold as possible, liberally apply a stain remover to the moldy portion of the clothing. Stain removers need time to soak into the fabric, so wait at least 30 minutes before washing the garment.  Commercial stain removers are readily available. Check the cleaning products aisle at your local grocery store or any supermarket. Run your washing machine on a “large” or “extra-large” load size, and set the water temperature to “hot.” Do not add any other items of clothing to the washing machine, as you’ll risk transferring mold spores to currently non-moldy clothes. If your washing machine estimates what load size is necessary based on the amount of fabric in the machine, throw in a few old rags or towels for weight. Once the laundry machine has filled with water, you can add vinegar to ensure that the mold is removed. Pour in ¾ cup (177 mL) of white vinegar to your load of laundry. Vinegar will also remove any unpleasant mildew smell that the moldy clothes have accumulated. You won’t be able to tell if the mold has been completely removed from the clothing until after it’s dried and the fabric has returned to its natural color. Let the fabric air dry on a flat surface or over a drying rack or drying line.  If it’s a nice day, you could also dry the item of clothing outdoors, in full sunlight. The sun’s added heat will help kill off and remove whatever mold remains on your clothing. Avoid using the dryer. Wait until the item is air-dried to check for any mold, discoloration, and odd smells. Putting any fabric with mold issues into the dryer risks contaminating the dryer with mold spores.

Summary:
Scrub off the mold using a toothbrush. Apply a stain remover to the mold. Wash the item by itself with hot water. Add vinegar to the laundry.  Air-dry the clothing.