Silicon Dioxide
The short version
An amorphous silica powder used as an anti-caking agent in powdered foods, table salt, and spices.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Safety profile
ADI not specified by JECFA. EFSA re-evaluated it in 2018 and completed a follow-up in 2024 that added a nano-scale risk assessment. It used a margin-of-exposure approach instead of setting an ADI, and concluded that E 551 does not raise a safety concern in any population group, including infants under 16 weeks. Crystalline forms are not permitted in food. Inhalation of any silica powder is hazardous regardless of form.
Sources
- EFSA — Re-evaluation of silicon dioxide (E 551) in foods for infants below 16 weeks and follow-up of its re-evaluation for all population groups, plain-language summary (17 October 2024; EFSA Journal 2024;22(10):8880) — European Food Safety Authority (EFSA), 2024. 2024 follow-up completed; no ADI set (MOE approach, nano-scale assessment); no safety concern
- WHO JECFA database — Silicon dioxide, amorphous (INS 551), evaluations 1985, 2015, 2017 — WHO / Joint FAO/WHO Expert Committee on Food Additives, 2017. JECFA ADI not specified
- 21 CFR 172.480 — Silicon dioxide, eCFR current as of 2026-10-13 — U.S. eCFR (Office of the Federal Register / GPO), 2026. US anticaking use limited to 2% of food; beer stabilizer
Checked against these sources on .
Educational information only. Not medical, dietary or veterinary advice. Spotted an error? Tell us.