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E551 Silicon Dioxide

E551Anti-caking agentsOrigin: Mineral
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The short answer
Silicon dioxide (E551) is a purified form of silica that keeps powders and spices from clumping. It's considered safe in food and passes through the body, though EFSA wants more data on its smallest particles.
Use in moderation

Safe in small amounts; may bother some people or raise blood sugar.

E-numberE551
Comes fromMineral
What it doesAnti-caking agents
Glycemic index—
Daily limitNot set
Also calledSilicon dioxide, Silica

Rules by country

🇺🇸 US FDAApproved with limits
🇪🇺 European UnionApproved with limits
🇨🇦 Health CanadaApproved with limits
CaliforniaNo extra rules

Approved in the US up to 2% of a food's weight. Approved in the EU and Canada with limits. EFSA's 2018 review found no sign of harm but could not set a daily limit because of data gaps on nano-sized particles.

Daily limit: Experts haven’t set a number because normal food amounts are far below any level of concern.

What is it?

Silicon dioxide is a fine, absorbent mineral powder. A small amount soaks up moisture so salt, spices and powdered drinks keep pouring freely.

Where it comes from: Made from sand: sodium silicate is processed into a fine, purified powder of amorphous silica. It's the same compound as quartz, in a non-crystalline form.

Why it’s in food

  • Stops salt and spices from caking
  • Keeps powdered drinks and supplements free-flowing
  • Helps shredded cheese and powdered sugar pour

Often found in

Spice blendsTable saltPowdered drink mixesProtein powdersSupplementsCoffee creamer

Also listed as: Silicon dioxide, Silica, Amorphous silica, Fumed silica, Precipitated silica

Health & gut impact

NanoparticlesUnder study

Food silica contains some nano-sized particles. EFSA found no harm but asked for better studies before setting a limit.

EFSA Panel on Food Additives (2018)

Not crystalline silicaBenefit

The lung disease linked to silica comes from breathing crystalline dust at work. Food silica is amorphous and eaten, not inhaled.

IARC Monographs Vol. 68 (1997)

What can I use instead?

Uncooked rice grains

Ratio: A few grains per shaker

Best for: Keeping salt dry at home

Airtight storage

Ratio: N/A

Best for: Homemade spice blends

Related

More anti-caking agents:

Calcium Phosphates (Tricalcium Phosphate) E341Calcium phosphates (E341) keep powders flowing, make baking powder rise and add calcium to plant milks. They're safe for most people, but phosphate additives add up, which matters for anyone with kidney disease.Use in moderation

Common questions

Is Silicon Dioxide safe?

Use in moderation (80/100). Approved in the US up to 2% of a food's weight. Approved in the EU and Canada with limits. EFSA's 2018 review found no sign of harm but could not set a daily limit because of data gaps on nano-sized particles.

Is Silicon Dioxide vegan?

Yes.

Is Silicon Dioxide gluten-free?

Yes.

Is silicon dioxide just sand?

It's the same compound as sand, but food-grade silica is a purified, non-crystalline powder. It passes through your body and is not the crystalline dust that harms lungs.

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Scientific sources & regulatory citations
  • 21 CFR 172.480 (US FDA)
  • EFSA OpenFoodTox: E551
  • EFSA Panel on Food Additives (2018)
  • IARC Monographs Vol. 68 (1997)

Last checked against FDA, EFSA and Health Canada records: October 31, 2026 · INS 551 · CAS 7631-86-9