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Metabilsulfite (Br.E. metabisulphite) refers to a range of compounds that contain a metal ion ionically bonded to the bisulfite anion (S2O5). The two most common metabisulfites are Sodium metabisulfite and Potassium metabisulfite which are dealt with in greater detail below.

Sodium metabisulfite[]

Sodium metabisulfite (Br.E. potassium metabisulphite) or E223 is a white, crystalline, inorganic compound with molecular formula Na2S2O5.

Potassium metabisulfite[]

Potassium-metabisulfite skeletal

Potassium metabisulfite.

Potassium metabisulfite (Br.E. potassium metabisulphite) or E224 is a white, crystalline, inorganic compound with molecular formula K2S2O5.


Metabisulfite is a common cause of allergic reactions in those who are sensitive to sulfites, causing respiratory reactions (wheezing) in both asthmatics and those who do not identify with the condition, in addition to other possible allergic reactions. Food or drink products containing either potassium or sodium metabisulfite will often have an allergy warning on the packet stating that the product contains sulfites but this is not always the case. Anyone with a known allergy to sulfites should avoid consuming a product that lists either potassium metabisulfite or sodium metabisulfite amongst its list of ingredients.