Mysterious Stains on Carpet
Article Originally From Michigan State University
Benzoyl Peroxide - Yellow or Orange Spots: This strong bleaching chemical is used in acne medications, age creams, some foot care products, and some pet shampoos. It's not water soluble and hard to wash off hands and face. Spots may show up in hours or not until months later depending on temperature and humidity. Most spots start as orange or dark yellow, and get lighter over time. On blue carpets they may be pinkish or white.
Bleaches - Yellow or Green: Oxygen bleaches act more slowly then chlorine bleach but both will fade dyes. So will swimming pool chemicals (calcium hypochlorite) tracked into the home, and mildew inhibitors that contain bleach if not used according to directions. Chlorine usually causes yellow spots, but will turn some red dyes to green.
Acids - Pink or orange spots on carpets are caused by as little as 1% hydrochloric acid in solution. Stomach acid is 10% stomach acid, so vomit must be cleaned up promptly and neutralized with a mild alkali such as a detergent solution and rinsed, or there will be permanent colored spots. It can turn some red dyes to bright blue. Toilet bowl cleaners, corn and callus removers, tile cleaners, and some rust removers also contain acids. Strong acids can cause red spots on tan/beige carpets.
Alkalis - Strong alkali as lye in oven cleaners and drain cleaners can change colors, and also destroy the textile. Remove, then neutralize spot with white vinegar solution, and rinse.
Furniture Polish - This can destroy red carpet dyes and cause green or blue spots. This usually happens where polish has gotten on carpet around the base of furniture by careless spraying or wiping, and is not found until furniture is moved.
Insecticides - Spraying insecticides on baseboards and getting the insecticide on the carpet can fade carpet dyes. Most often cited in this are malathion, diazinon, and DDVP.
Phenol Disinfectants - Some, not all, phenols in disinfectants and germicides, fade carpets. Some bathroom cleaners contain phenols; read label.
Plant Foods - Yellow Spills of liquid plant foods or leakage from house plants can discolor carpet. Spots are usually dull yellow. They start down near the backing and develop up into the pile, sometimes taking months to show up.
Urine - Urine stains discolor carpet and upholstery, as well as causing a musty odor. Spots turn dull yellow or red.