Directly from the FDA's website (link below)
FALCPA's labeling requirements extend to retail and food-service establishments that package, label, and offer products for human consumption. However, FALCPA's labeling requirements do not apply to foods that are placed in a wrapper or container (such as paper or a box for a sandwich) following a customer’s order at the point of purchase.
Consumers may also see advisory statements such as “may contain [allergen] or “produced in a facility that also uses [allergen].” These are used to address “cross-contact,” which can occur when multiple foods with different allergen profiles are produced in the same facility using shared equipment or on the same production line, as the result of ineffective cleaning, or from the generation of dust or aerosols containing an allergen.
FDA guidance for the food industry states that advisory statements should not be used as a substitute for adhering to current good manufacturing practices and must be truthful and not misleading.
Does FALCPA require food manufacturers to label their products with advisory statements, such as "may contain [allergen]" or "processed in a facility that also processes [allergen]?"
No. FALCPA does not address the use of advisory labeling, including statements describing the potential presence of unintentional ingredients in food products resulting from the food manufacturing process. FALCPA does require FDA to submit a report to Congress, a part of which assesses the use of, and consumer preferences about, advisory labeling. In earlier guidance, FDA advised that advisory labeling such as "may contain [allergen]" should not be used as a substitute for adherence to current Good Manufacturing Practices (cGMPs). In addition, any advisory statement such as "may contain [allergen]" must be truthful and not misleading.
Does FALCPA require FDA to set so-called thresholds for any food allergen?
FALCPA does not require FDA to establish a threshold level for any food allergen. It is not unlikely, however, that FDA will at some point need to consider a threshold level for one or more food allergens in the context of reviewing a petition or a notification submitted to request that an ingredient be exempt from FALCPA's labeling requirements.https://www.fda.gov/...rgens-edition-4
Processed in a Facility That Also Processes…
It’s not uncommon to see an allergen statement like this on a packaged food. But what does it mean?
According to the FDA this is known as a May Contains claim. This type of claim is not required, nor is it recommended by the FDA.
So what if a food company produce their product in a facility that also processes other allergens? It shouldn’t matter that other allergens are present in the facility — proper cleaning and production should prevent any allergen cross contact.
A “may contains” claim doesn’t mean much — it is a tool to limit business liability for any allergens that show up in your product. But don’t rely on this type of claim to compensate for bad food processing practices. While it may stop someone with a food allergy from eating your product, it will not mean that a food business is exempt from liability related to allergens in your product.