Processing red flags
Silicon dioxide
Definition
What it is
Silicon dioxide (silica, E551): anti-caking agent; EFSA raised concerns in 2018 about nanoparticle forms being absorbed and accumulating in tissue; routine low-dose exposure is considered safe.
On the label
Label names covered by this flag
- silicon dioxide
- silica
- synthetic amorphous silica
- e551
Regulation
Regulatory status
No bans or restrictions are recorded for this ingredient in the jurisdictions clearlabel tracks (US, EU, UK, Canada, Japan, Australia/NZ, Brazil).
Explainer
In plain language
Silicon dioxide, also called silica or E551, is a fine powder used to keep dry foods from clumping and to help powders flow. It occurs naturally in sand and quartz and is also made in a purified synthetic form for food use. Its whole job is to keep salt, spices, and powdered mixes from caking together.
Assessment
Why it is flagged
In 2018 EFSA re-evaluated silicon dioxide and could not fully rule out concerns because some food-grade material contains nanoscale particles, and the data on whether those particles are absorbed and accumulate in tissue was incomplete. EFSA later called for narrower specifications and further study rather than declaring the additive unsafe at normal food levels. Routine dietary exposure is generally considered low risk, and the FDA permits silicon dioxide as an anti-caking agent within limits. Clear Label marks it low severity because it is a processing marker and an open research question, not an established harm. It is the nanoparticle uncertainty, not day-to-day intake, that keeps it on the list.
In the aisle
Where it commonly shows up
- Table salt and seasoning blends
- Powdered drink mixes
- Grated and shredded cheese
- Powdered soups and gravy mixes
- Spice blends and dry rubs
- Some supplements and protein powders
Practical
Reading the label
US labels list it as silicon dioxide or silica; in the EU it appears as E551. It shows up most often in anything powdered or granulated that needs to stay free-flowing, including supplements where it is used in capsules and tablets.
FAQ
Common questions
Is silicon dioxide the same as the silica gel packets in packaging?
They are chemically related, but the silica gel packets in shoeboxes and vitamin bottles are a desiccant not meant to be eaten. The food additive is a purified, food-grade form used in tiny amounts.
Why did EFSA raise concerns in 2018?
EFSA noted that some food-grade silicon dioxide contains nanoscale particles and that the evidence on whether they are absorbed or accumulate was incomplete. It asked for tighter specifications and more study rather than banning the additive.
Is it safe at the amounts used in food?
Regulators consider routine low-dose exposure to be low risk, and the FDA and EU both permit it. The unresolved part is the long-term effect of nanoscale forms, which is why it stays on Clear Label as a processing marker.
Citations
Sources
Citation
Primary reference
About this page: the definition, label names, severity, and regulatory chips come from the clearlabel ingredient taxonomy, the same data the scanner uses to score products. Research summaries describe associations reported in published studies, not diagnoses; individual responses vary. Scan any product with clearlabel to see which of its ingredients carry flags.