You can buy sodium thiosulfate crystals at drug stores or photography supply stores.
Do not use a clothes dryer when attempting to remove a Betadine stain, or you will fix the stain permanently in the fabric.
Betadine is an iodine-based antimicrobial available as an ointment, swab, tincture or skin cream. People generally use Betadine cream on minor scrapes and cuts to prevent infection. Medical professionals also use Betadine as a topical antiseptic before and during sterile surgical procedures. Like other iodine-based products, Betadine can stain your skin and clothing. You can easily remove these stains from your skin with alcohol swabs, but removing them from your clothing can be a challenge.
Determine whether the fabric is washable or nonwashable. Most cotton and polyester blends are washable, and have washing instructions on the garment label. Consult a laundry specialist for labels that say “dry clean only,” because these fabrics usually require professional cleaning.
Flush the Betadine from the fabric by rinsing the reverse side of the stain with cold running water. Do not flush the stain with hot water, because heat will permanently set the stain in the clothing fibers. After rinsing, keep the stained area moist to prevent the stain from setting.
Soak a cotton ball in a 3-percent hydrogen peroxide solution, which is available at most pharmacies and supermarkets. Blot the stain with the peroxide-saturated cotton until you have transferred as much Betadine as possible from the garment to the cotton ball. Hold the stained area under cold running water to flush the hydrogen peroxide from the clothing fibers.
Soak a cotton ball in rubbing alcohol. Lay the garment on a hard surface and gently blot the stain with the alcohol-saturated cotton. Replace the cotton ball with a new alcohol-soaked ball and repeat this process until you have removed as much of the stain as you can.
Make a solution comprising 1 qt. of cold water, 1 tbsp. of ammonia and 1 tsp. of bleach-free liquid laundry detergent. Use a detergent that contains cleaning enzymes if possible, because these enzymes will help to break down the stain. Soak the garment in this solution for 30 minutes, and then wash it as usual without drying.
Make a solution for stubborn Betadine stains by mixing 1 tbsp. of sodium thiosulfate crystals with 1 cup of cool water, and stirring until the crystals completely dissolve. Soak a clean white cloth in this solution and use it to saturate the stain thoroughly. Let the solution sit on the fabric for 10 minutes, and then rinse the garment well to remove the cleaning agent from the fabric.