You will see warnings like 'May contain peanuts,' 'Made in a facility that also processes tree nuts,' or 'Processed on shared equipment with wheat' on thousands of packaged foods. These are called precautionary allergen labels (PAL) or advisory statements — and they are one of the most misunderstood phrases in food allergy. The most important thing to know: they are entirely voluntary under US federal law, and there is no regulated threshold that requires a company to add one.
What US law actually requires (and does not)
FALCPA (the Food Allergen Labeling and Consumer Protection Act of 2004) requires manufacturers to declare the intentional presence of any of the 9 major allergens in a food. It does not require disclosure of unintentional cross-contact — allergen residue that ends up in a product due to shared production lines, equipment, or facilities. Precautionary labels like 'may contain' are a voluntary industry practice, not an FDA requirement. As of the writing of this guide, the FDA has not established a minimum trigger threshold — a manufacturer decides for itself when to add such a statement (FDA).
What 'may contain' and similar phrases actually communicate
Per FARE guidance, these statements signal that there is a real possibility of cross-contact — i.e., an allergen could have ended up in the product during manufacturing, even though it is not an intentional ingredient. What they do not tell you: how much allergen may be present, how likely contact actually was, or whether the risk differs between 'may contain' and 'made in a facility with.' Those three phrases vary in specificity (shared facility > shared line > shared equipment) but none carries a standardized legal meaning. FARE recommends that people with food allergies treat all three warnings with equal caution unless they have direct confirmation from the manufacturer about their specific cross-contact controls.
The absence of a warning is not a guarantee
Because these labels are voluntary, a product that carries no advisory statement is not necessarily free of cross-contact — the manufacturer may simply have chosen not to add one. FARE notes that some companies voluntarily add these warnings as a precaution even when cross-contact risk is low; others with genuinely higher risk do not add them at all. If cross-contact risk matters to you, the most reliable step is to contact the manufacturer directly and ask about their allergen control practices.
FDA Top-9 Allergen Reference
See all 9 FDA major allergens and their label names
Open FDA Top-9 Allergen Reference →A 'may contain' warning signals possible cross-contact, but is voluntary — no threshold is regulated. Its absence is not a guarantee of safety. For high-stakes decisions, contact the manufacturer.