Most anti-caking agents used in everyday foods are not harmful at the levels you’re actually consuming. These additives make up a tiny fraction of any product, typically capped at 1 to 2 percent by weight, and in many cases far less. That said, not all anti-caking agents are equal. A few deserve more scrutiny than others, and one has already been pulled from the food supply in Europe.
What Anti-Caking Agents Actually Do
Anti-caking agents keep powdered and granulated foods from clumping together. Without them, your table salt would turn into a solid block in humid weather, powdered sugar would cement itself into a brick, and instant soup mixes would be impossible to pour. They work by absorbing moisture or coating individual particles so they slide past each other freely.
You’ll find them in salt, spice blends, garlic and onion salt, baking powder, powdered coffee creamers, grated cheese, icing sugar, dry soup mixes, seasoning packets, and protein powders. The most common ones include silicon dioxide (listed as E551 in Europe), calcium silicate, sodium aluminosilicate, tricalcium phosphate, and magnesium stearate.
Silicon Dioxide: The Most Widely Used
Silicon dioxide is the anti-caking agent you’ll encounter most often. It’s essentially a purified form of silica, the same compound that makes up sand and quartz. In the U.S., it’s limited to no more than 2 percent of a food’s weight. In practice, most products contain far less.
Animal studies have looked at whether silicon dioxide causes intestinal damage. In one study published in Environmental Health Perspectives, mice given silicon dioxide at doses up to 100 mg per kilogram of body weight for 60 days showed no changes in intestinal permeability. Their gut lining stayed intact. However, in a separate arm of the same study using mice genetically prone to gluten sensitivity, silicon dioxide at a lower dose worsened the inflammatory response after gluten exposure: the intestinal lining showed structural changes and elevated immune cell counts. This suggests that silicon dioxide may interact differently in people who already have a sensitive gut.
One concern that comes up in toxicology research is particle size. A portion of food-grade silicon dioxide exists as nanoparticles, which are small enough to pass through intestinal tissue. A study in Colloids and Surfaces B found that nanoparticle-sized silica had an oral absorption rate of about 4 percent, compared to roughly 3 percent for larger particles. Both numbers are low, and the study found no meaningful difference in how the body distributed or eliminated the particles once absorbed. For most people eating normal amounts of processed food, this is not a practical concern.
Aluminum-Based Agents Raise More Questions
Sodium aluminosilicate and other aluminum-containing anti-caking agents are a different story. Aluminum is a known neurotoxin at high doses, and the body removes it slowly from brain tissue. About 38 percent of ingested aluminum accumulates in the intestinal lining, and chronic exposure has been linked to cognitive impairment in occupational studies, where workers showed measurable declines in concentration, learning, and memory.
The strongest evidence for aluminum’s neurotoxicity comes from dialysis patients, who developed memory impairment, dementia, and disorientation after prolonged exposure through contaminated dialysis fluid. Their blood and brain tissue contained elevated aluminum levels. Research has also connected aluminum to changes in brain cells that mirror what happens in Alzheimer’s disease: it promotes the buildup of the same toxic protein clumps found in Alzheimer’s patients and damages the nerve cells most important for memory.
The amounts of aluminum you get from an anti-caking agent in table salt are far smaller than what those dialysis patients were exposed to. But aluminum also enters your body through antacids, cookware, drinking water, and other food sources, so it adds up. People with kidney disease are especially vulnerable because they can’t efficiently clear aluminum from their bodies. If you want to minimize exposure, checking labels for sodium aluminosilicate or aluminum calcium silicate is a reasonable step, particularly if you use a lot of seasoning blends or processed salt.
Titanium Dioxide: Banned in Europe
Titanium dioxide (E171) was once used as both a whitening agent and anti-caking agent in candies, chewing gum, sauces, and supplements. In 2021, the European Food Safety Authority concluded that titanium dioxide could no longer be considered safe as a food additive. The core issue: scientists could not rule out that titanium dioxide particles damage DNA after being consumed. Because of this genotoxicity concern, EFSA was unable to establish any safe daily intake level.
The European Union subsequently banned titanium dioxide in food. The U.S. Food and Drug Administration has not followed suit, so E171 remains legal in American products. If this concerns you, it will appear on ingredient labels as “titanium dioxide” or E171.
Allergic Reactions Are Rare but Documented
True allergic reactions to anti-caking agents are uncommon, but they do happen. Lecithin (E322), derived from soy or eggs, is sometimes used as an anti-caking agent and can trigger reactions in people with soy or egg allergies. In clinical testing, as little as 50 mg of egg lecithin caused a skin rash in a child with eczema, and 100 mg of soy lecithin triggered a facial rash in a child with peanut allergy. Bakery workers exposed to soy lecithin dust have also reported asthma attacks.
These reactions are tied to the protein source (soy, egg) rather than the anti-caking function itself. If you have a known food allergy, checking whether lecithin appears on the label and identifying its source matters more than worrying about anti-caking agents as a category.
How Much You’re Actually Eating
Regulatory limits keep anti-caking agents to small percentages of any food. In the U.S., both silicon dioxide and calcium silicate are capped at 2 percent of a food’s weight, with baking powder allowed up to 5 percent. In Canada, salt can contain up to 1 percent anti-caking agents (2 percent for fine-grained salt), and icing sugar up to 1.5 percent. Some agents, like ferrocyanide compounds used in salt, are restricted to just 13 parts per million.
To put this in perspective: if you use a teaspoon of table salt in a day, the anti-caking agent in it weighs less than a single grain of rice. Even people who eat heavily processed diets are getting these substances in amounts that are orders of magnitude below the doses used in animal toxicity studies.
Cleaner Alternatives Exist
If you’d rather avoid synthetic anti-caking agents entirely, you have options. Some brands use rice hulls or rice concentrate as a natural alternative to silicon dioxide and tricalcium phosphate. These show up on labels simply as “rice concentrate” or “rice hull extract” and perform the same anti-clumping function. Cornstarch and tapioca starch also serve as anti-caking agents in products like shredded cheese and icing sugar.
Buying unprocessed versions of common foods sidesteps the issue altogether. Sea salt and kosher salt often contain no anti-caking agents. Freshly grated cheese doesn’t need the cellulose or starch coating that pre-shredded bags require. Whole spices ground at home won’t have any additives at all. These choices won’t transform your health on their own, but they’re straightforward swaps if minimizing additives is a priority for you.