Yes. Under US law, a food ingredient that contains protein derived from milk counts as the major food allergen milk, so a packaged food made with whey has to name milk on its label. The label can do it in a “Contains” statement beside the ingredient list, or in parentheses after the ingredient, as in “whey (milk).”

In 2026, FDA sent warning letters to two food makers whose labels did neither: a New Jersey bakery whose rolls had whey in the dough, and a Los Angeles maker of whey protein isolate. This article sets out the rule, what each letter found, and how to check a label for the same gap.

Why whey counts as milk on a US food label

The Federal Food, Drug, and Cosmetic Act defines “major food allergen” in 21 U.S.C. 321(qq). Its first paragraph names nine foods: “Milk, egg, fish (e.g., bass, flounder, or cod), Crustacean shellfish (e.g., crab, lobster, or shrimp), tree nuts (e.g., almonds, pecans, or walnuts), wheat, peanuts, soybeans, and sesame.” The Food Allergen Labeling and Consumer Protection Act of 2004 named the first eight, and the FASTER Act of 2021 added sesame, effective January 1, 2023.

The second paragraph is the one that catches whey. A major food allergen is also “a food ingredient that contains protein derived from” one of those nine foods. FDA’s letter to the protein maker calls whey “a protein derived from milk.” On a label, then, whey is milk, as is any other ingredient that carries milk protein, whatever its name.

The definition carves out highly refined oils derived from those foods, which FDA’s guidance describes as “refined, bleached, deodorized oils,” and ingredients derived from them. An individual ingredient can also be exempted through a petition or a notification filed with FDA. Beyond that, FDA states that it “has not established a threshold level for any allergens.”

The rule covers most packaged foods FDA regulates, dietary supplements included, but not cosmetics. It also reaches the small additions to a formula: section 343(w)(4) applies it to “a flavoring, coloring, or incidental additive” that contains a major food allergen, although incidental additives such as processing aids are otherwise exempt from the ingredient list.

The two ways a label can declare milk

Under 21 U.S.C. 343(w)(1), a food other than a raw agricultural commodity that is or contains a major food allergen is misbranded, the Act’s term for a food whose labeling breaks its rules, unless the label names the allergen’s food source in one of two ways:

• A “Contains” statement. The word “Contains,” followed by the name of the food source, “printed immediately after or is adjacent to the list of ingredients,” in type no smaller than the list’s. For a product made with whey, that is “Contains milk.”
• A parenthetical in the ingredient list. The ingredient’s name “is followed in parentheses by the name of the food source.” The statute describes the form without an example. “Whey (milk)” is FDA’s own example, used in both letters and on its Food Allergies page.

The parenthetical is not needed when the ingredient’s own name already uses the food source’s name, as buttermilk does, or when that name appears elsewhere in the list, other than inside an excepted ingredient such as a highly refined oil. Whey does not name its source, so “whey” alone does not declare milk.

FDA’s guidance adds one point about the first method. If a label uses a “Contains” statement, it “is to include the names of the food sources of all major food allergens used as ingredients,” including those the list already declares. Its example is a list with sodium caseinate, whey, egg yolks and natural peanut flavor, which calls for “Contains milk, egg, peanuts.”

What FDA’s two 2026 warning letters found

A warning letter is FDA’s written notice to a company of violations it has found, in both these cases at inspection. Both letters cite section 403(w) of the Act, which is 21 U.S.C. 343(w).

The bakery letter, dated May 20, 2026, followed an inspection in August 2025. FDA found that two of the bakery’s kaiser roll products “are manufactured with whey, but the label does not list the major food allergen milk.” A second finding goes one step earlier. The investigator was told “the same ingredients were used for all your products,” and FDA wrote that “the dough formulation includes the ingredient whey, but it is not declared in the ingredient statement.” The ingredient list left out the whey itself, and the milk with it.

In the letter to the protein maker, dated February 10, 2026, FDA found that the label of its Whey Protein Isolate “fails to declare the major food allergen, milk,” although the product “is manufactured using whey.” Whey was in the product’s own name, and the label still did not name milk. The same letter found that the label left out sunflower lecithin, “one of the two components of the bulk ingredient” used to make it.

Both letters also cite FDA’s preventive controls rule for food facilities. Under 21 CFR 117.135(c)(2), a facility’s food allergen controls include those for “labeling the finished food, including ensuring that the finished food is not misbranded under section 403(w),” next to those protecting food from allergen cross-contact, an allergen getting into a product by accident.

Milk is not a rare case. FDA’s Food Allergies page says that, of the major food allergens, “milk represents the most common cause of recalls due to undeclared allergens,” and lists bakery products among the five food types most often involved in allergen recalls.

Where the declaration goes missing

In neither case was the milk hidden. It was in a dough formula, and in a product’s own name. What failed was the step that carries what each ingredient is made of onto the label.

That step runs on documents. A label is built from the formula, and the formula from ingredients whose composition the supplier’s specification or allergen statement sets out. An ingredient whose name does not say its source, such as whey or sodium caseinate, depends on someone carrying that knowledge forward, and so does a compound ingredient. FDA’s guidance gives the case of a spice mix with wheat flour as an anticaking agent: the wheat must still be declared on the finished food, even where the mix is listed only as “spices.”

The requirement also travels between companies. FDA’s guidance says allergen labeling applies to bulk containers “shipped for further processing, labeling, or repacking,” and that the regulations letting a written agreement exempt such a shipment from most labeling “do not provide an exemption for food allergen labeling requirements.”

The same reading problem in cosmetics

EU cosmetics law has a parallel. Under Article 19(1)(g) of Regulation (EC) No 1223/2009, a fragrance appears in the ingredient list as “parfum” or “aroma,” and the fragrance allergens listed in Annex III, a list extended by Regulation (EU) 2023/1545, must be named as well once they exceed 0.001% of a leave-on product or 0.01% of a rinse-off one. “Parfum” does not say which allergens are inside. In practice the names come from the fragrance supplier’s declaration, as the article on EU fragrance allergen labeling sets out.

How to check a label for milk and the other major allergens

The check runs one ingredient at a time, from the formula to the printed label:

• Start from the current formula, not the last label. List every ingredient, including the components of compound ingredients and any flavoring, coloring or processing aid.
• For each one, record from the supplier’s specification or allergen statement which of the nine major food allergens, if any, it contains.
• Check each name. Nonfat dry milk declares itself. Whey and sodium caseinate need “(milk)” after them, milk named elsewhere in the list, or a “Contains” statement.
• If the label has a “Contains” statement, check that it names every major food allergen in the product.
• For tree nuts, fish and Crustacean shellfish, check that the label names the specific nut or species, as 21 U.S.C. 343(w)(2) requires.
• Treat an oil as excepted only if the supplier’s documents say it is highly refined.
• Where one printed label serves several products, check it against each product’s formula. The bakery letter notes two such shared labels.
• Recheck whenever a formula, an ingredient or a supplier changes.

The milk in both products was in plain view. A label is only as right as the reading that carries what each ingredient is made of onto it.