Undeclared allergens: why “safe” foods sometimes aren't
A product your family has eaten for years can quietly change. Here's how allergen recalls happen and how to stay a step ahead.
By the Recall Radar team, September 22, 2026, 6 min read
The short version
- U.S. law requires nine major allergens to be declared on food labels.
- Undeclared allergens are one of the most common reasons foods are recalled.
- Recipes and suppliers change, so re-read labels even on familiar products.
- “May contain” statements are voluntary and don't follow a single standard.
For families managing food allergies, the scariest products aren't the unfamiliar ones. They're the trusted ones: the granola bar or frozen meal you've bought a hundred times. When those go wrong, it's usually because of an undeclared allergen.
The nine major allergens
In the United States, food labels must clearly declare nine major allergens: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame. Sesame was added most recently, with the requirement taking effect in 2023.
How allergens end up undeclared
- Packaging mix-ups. A product goes into the wrong wrapper, such as a peanut variety packed in a plain-flavor bag.
- Recipe or supplier changes. An ingredient is reformulated and the label isn't updated in time.
- Shared equipment. Residue from one product line ends up in another.
- Ingredients within ingredients. A seasoning blend or flavoring supplied by another company contains an allergen that wasn't passed on.
Undeclared allergens are consistently among the most common causes of food recalls in the U.S., and for someone with a severe allergy, they can be life-threatening.
The trouble with “may contain”
Statements like “may contain tree nuts” or “made in a facility that also processes peanuts” are voluntary. There's no single standard for when they're used, so their absence doesn't guarantee a product is free of cross-contact. Talk to your allergist about how your family should treat them.
Habits that help
- Re-read the label every time, even on products you know well. Packaging changes are a warning sign.
- Keep the packaging (or a photo of the lot code) until the product is used up.
- Carry prescribed epinephrine and make sure caregivers and schools know the plan.
- Track allergies for each person in the household, not just “the family”.
This article is general information, not medical, veterinary or legal advice. Always follow the instructions in the official recall notice and talk to a professional about your situation.