Sodium metabisulfite is a food additive, not edible, accidental consumption will cause harm to the human respiratory tract and digestive tract. 1. Sodium metabisulfite is used as a preservative, bleaching agent and loosening agent in the food processing industry, but when used as a bleaching agent, it can only be used for fumigation, and cannot be directly immersed in the surface of objects. Sodium metabisulfite decomposition in the air, will produce sulfur dioxide, sulfur dioxide is a kind of irritating odor of the gas, will be on the human respiratory tract, digestive tract mucous membrane damage, cause irritation cough or asthma. 2. Sodium metabisulfite dissolved in water will produce sulfurous acid, misuse will cause corrosive damage to the intestinal tract, and will cause damage to the liver and kidney function, serious cases can cause acute poisoning, or even death.