Sulfites/sulphites are substances that occur naturally in the human body due to the metabolism of amino acids containing sulfur in their side chains. They are readily oxidized to sulfates via enzymatic reactions and excreted in urine at the rate of 1000 mg/day. Sulfites are often considered as allergens due to adverse symptoms observed in asthmatic patients. Exogenous sources of sulphites include polluted air, food and beverages containing sulphur dioxide (SO2). SO2 is a molecule that easily reacts with several small compounds including aldehydes, ketones, anthocyanins, cobalamine, thiamine, NAD, flavins, among others. SO2 also interacts with cysteine residues in proteins and promotes cross-linking. Sulfites are also used as regulated food preservatives/additives/enhancers in dried fruits, wine, beer, etc. They are considered as GRAS (Generally Recognized as Safe) in food and beverages. In wine, SO2 reacts with sugars, aldehydes and anthocyanins. The term sulfite is used for all sulfite-derived molecules: bisulfites, metasulfites, and SO2. Total sulfite is defined as the sum of bound and free sulfite. Total Sulfite Assay kit is a simple and sensitive assay to detect small concentrations of sulfites in a variety of food and beverage samples. This assay is based on the oxidation of sulfite to sulfate producing a stable signal at 570 nm, which is directly proportional to the amount of sulfite in the sample. This assay is very sensitive and can detect as low as 20 μM of sulfite in a variety of samples.