Potassium Metabisulfite

CAS 16731-55-8 · E224 · potassium pyrosulfite · potassium disulfite

The main sulfite used in winemaking and home brewing ("Campden tablets"), also in cider and juices. It releases SO2 to prevent spoilage. Safe for most people but a trigger for sulfite-sensitive and asthmatic individuals; FDA requires labeling at 10 ppm or more.

high confidence

Researched July 7, 2026

Specimen 0217Potassium Metabisulfite

Concerns

Potassium metabisulfite acts as a sulfiting agent (releasing sulfur dioxide), so it can provoke reactions in sensitive individuals — especially asthmatics (roughly 3-10% react) — ranging from dermatitis, flushing, hypotension, abdominal pain and diarrhea to rare life-threatening asthmatic and anaphylactic reactions (Vally & Misso; Vally et al.)
FDA requires sulfiting agents present at 10 ppm or more in a finished food to be declared on the label (21 CFR 101.100) and prohibits sulfites on fruits and vegetables sold or served raw
EFSA's 2016 group re-evaluation set only a temporary ADI of 0.7 mg SO2 equivalents/kg body weight per day; in 2022 EFSA withdrew this temporary ADI, concluding the toxicity database was inadequate to establish a safe intake level

Regulatory flags

⚑IARC Class: NL
⚑EDC Status: None
⚑Regulatory: US: GRAS w/ mandatory labeling >=10 ppm (21 CFR 101.100), banned on raw produce (1986); EU: E224, group ADI withdrawn (EFSA 2022)
⚑Evidence Grade: A

Commonly found in

Wine (Campden tablets)CiderDried fruitFruit juicesHome brewing

Sources & references

Last researched: July 7, 2026

Research disclaimer: This rating is based on available peer-reviewed research and regulatory assessments at the time of publication. It is not medical advice. Consult a qualified professional for personal health or skin concerns.

Check another ingredient

Search our database of scored cosmetic, food, and household ingredients — or scan a full product label.

Open the Ingredient Lab