Sodium sulfite (E221) on your skin: a safety profile
Low risk(People-specific data is limited; this page draws from human adult context.) Sodium sulfite (E221) presents low risk to human adults. Part of the sulfite class with EFSA group ADI 0.7 mg SO2 equivalents/kg/day; sodium sulfite provides ~50.4% SO2 equivalents by weight. No carcinogenicity classification. In healthy adults with normal sulfite oxidase activity, dietary sodium sulfite is efficiently metabolized to sulfate and excreted. The key safety concern is class-wide sulfite sensitivity (see E220) affecting ~1% of adults and up to 10% of asthmatics. Sulfite oxidase (SUOX) deficiency is an extremely rare genetic disorder causing sulfite accumulation; not a general population safety concern.
What is sodium sulfite (e221)?
The IUPAC name is disodium;sulfite.
Also known as: disodium;sulfite, SODIUM SULFITE, Disodium sulfite, Sodium sulfite anhydrous.
- IUPAC name
- disodium;sulfite
- CAS number
- 7757-83-7
- Molecular formula
- Na2O3S
- Molecular weight
- 126.05 g/mol
- SMILES
- [O-]S(=O)[O-].[Na+].[Na+]
- PubChem CID
- 24437
Risk for people
Low riskSodium sulfite (E221) presents low risk to human adults. Part of the sulfite class with EFSA group ADI 0.7 mg SO2 equivalents/kg/day; sodium sulfite provides ~50.4% SO2 equivalents by weight. No carcinogenicity classification. In healthy adults with normal sulfite oxidase activity, dietary sodium sulfite is efficiently metabolized to sulfate and excreted. The key safety concern is class-wide sulfite sensitivity (see E220) affecting ~1% of adults and up to 10% of asthmatics. Sulfite oxidase (SUOX) deficiency is an extremely rare genetic disorder causing sulfite accumulation; not a general population safety concern.
Regulatory consensus
3 regulatory and scientific bodies have classified Sodium sulfite (E221). The classifications differ — that's the data.
| Agency | Year | Classification | Notes |
|---|---|---|---|
| IARC | 2016 | Not evaluated by IARC for carcinogenicity — Sodium sulfite (E221; CAS 7757-83-7; Na2SO3; MW 126.04; anhydrous) is one member of the sulfite preservative class (E220–E228) and shares the group ADI of 0.7 mg SO2 equivalents/kg/day established by EFSA (2016 re-evaluation); sodium sulfite releases approximately 50.4% SO2 equivalents by weight; no IARC, EPA, or EFSA carcinogenicity classification; safety profile is dominated by the class-wide sulfite sensitivity concern described under E220 (sulfur dioxide); sodium sulfite is metabolized by hepatic and mitochondrial sulfite oxidase (SUOX enzyme, requiring molybdenum cofactor) to sulfate, which is excreted renally; SUOX deficiency is a rare inherited metabolic disorder where sulfite oxidase is absent or deficient, leading to accumulation of sulfite and sulfocysteine — highly toxic to the developing brain; in the general population with normal SUOX activity, dietary sulfite is efficiently detoxified | |
| EPA CTX / Genetox | — | Genotoxicity: positive (Ames: positive, 16 positive / 5 negative reports) | |
| EPA CTX / Genetox | — | Genotoxicity: positive (Ames: positive, 16 positive / 5 negative reports) |
Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.
Where you encounter sodium sulfite (e221)
- Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
- Occupational Environments — Factories, Warehouses, Transportation vehicles
- Personal Care — shampoo, conditioner, lotion, cosmetics, sunscreen
Safer alternatives
Lower-risk approaches that achieve a similar outcome to Sodium sulfite (E221):
-
Fragrance-free formulations
Trade-offs: Consumer preference for scented productsRelative cost: Lower (ingredient elimination)
-
Essential oil-based fragrances (with disclosure)
Trade-offs: Natural does not mean safe — many essential oils are skin sensitizersRelative cost: 2-5× conventional
Frequently asked questions
What products contain sodium sulfite (e221)?
Sodium sulfite (E221) appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments); shampoo (Personal care).
Why do regulators disagree about sodium sulfite (e221)?
Sodium sulfite (E221) has been classified by 3 agencies including IARC, EPA CTX / Genetox, EPA CTX / Genetox, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.
See Sodium sulfite (E221) in the body app
Look up products containing sodium sulfite (e221), compare to alternatives, and explore the full data record.
Open in body View raw API dataSources (1)
- Sodium Sulfite E221 CAS 7757-83-7 Na2SO3 Anhydrous 50.4% SO2 Equivalents; EFSA 2016 Group ADI 0.7 mg SO2 Eq/kg/day E220-E228 Class EFSA Journal 2016;14(4):4438; Sulfite Oxidase SUOX Mitochondrial Molybdopterin Cofactor Sulfate Renal Excretion; SUOX Deficiency Rare AR <1:100000 Neonatal Seizures Opisthotonus Neurodegeneration Sulfite Sulfocysteine Accumulation; Sulfite Sensitivity Class-Wide Asthmatic Bronchoconstriction Pharmacological Not IgE; Wine Beer Dried Vegetables Industrial Potato Processing; Pulp Paper Sulfite Pulping Lignin Delignification Largest Industrial Use; Water Treatment Dechlorination Boiler Feedwater; Textile Dye Stripping; Rapid Aerobic Oxidation Sulfate Half-Life <1h Environmental (2016) — regulatory
Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →