Silicon Dioxide

Additive · E 551

Silicon dioxide is a fine powder used to keep dry foods from clumping and to help powders flow. Food forms are made as amorphous silica. Their small particles can join into larger clusters; they differ from the crystalline silica found in some dust.

Also known as

silicon dioxide · silica · synthetic amorphous silica · amorphous silicon dioxide · colloidal silicon dioxide · fumed silica · pyrogenic silica · precipitated silica · silica gel · hydrous silica · E 551 · INS 551

Why PRūF tracks it

The review considers mouse intestinal immune findings and gaps in evidence about smaller particles and long-term human exposure; current studies do not establish food-level cancer, infertility, celiac disease or other clinical harm in people.

Read the research

Silicon dioxide helps powdered foods stay free flowing. Food additive E 551 is synthetic amorphous silica, and commercial samples contain tiny primary particles joined into larger clusters. Particle size, preparation and food conditions matter when comparing studies. A 2024 mouse study using food-grade material found changes in intestinal immune responses and reduced tolerance to a food protein, including when the additive was mixed into food.

A separate susceptible mouse model showed worse gluten-related intestinal injury; neither experiment establishes that eating E 551 causes food allergy or celiac disease in people. EFSA considered these findings and still found no safety concern at assessed uses and exposure levels, while identifying gaps in studies of smaller particles and human immune effects. A 2025 oral mouse study found no fertility or early embryo harm at its tested doses. Other nanoparticle experiments report effects under different, often much higher, exposures.

Human food-specific outcome evidence remains limited. Current US, EU and Canadian permissions have conditions; the international re-evaluation priority list is a request for further evidence, not a food ban.

Research reviewed on September 5, 2026 · 12 sources