Baby Ledger AIYou are holding a box of teething crackers. The ingredient list looks clean for your baby's confirmed milk allergy, but under it sits one small line: "May contain traces of milk." Is that a real warning, or just boilerplate every company prints to be safe?
Here is the part most parents were never told: US law treats those two parts of the label completely differently. The ingredient declaration is mandatory and regulated. The "may contain" line is voluntary, unregulated, and means whatever the manufacturer decided it should mean. This guide walks through the difference, the alternative ingredient names allergens hide behind, and how to turn a confusing label into a useful conversation with your child's allergist. It is informed by published guidance from the FDA and Food Allergy Research & Education (FARE).
The label has two kinds of allergen statements (only one is required)
US packaged-food labels regulated by the FDA carry allergen information in two very different layers.
Layer 1: the mandatory declaration. Under the Food Allergen Labeling and Consumer Protection Act (FALCPA, passed in 2004, in effect since January 1, 2006), any of the nine US major allergens actually used as an ingredient must be declared in plain English. The Big 9 are milk, egg, peanut, tree nuts, crustacean shellfish, fish, wheat, soy, and sesame - sesame became the ninth via the FASTER Act, mandatory since January 1, 2023. Note that "shellfish" here means crustaceans (shrimp, crab, lobster); mollusks like clams, squid, and scallops are not on the US major-allergen list.
Manufacturers have two compliant formats: name the source in parentheses inside the ingredient list, like "whey (milk)" or "lecithin (soy)", or add a "Contains" statement right after the list, like "Contains: milk, soy." The Contains statement itself is optional - a label with proper parenthetical declarations does not need one. But if a company uses one, it must list every major allergen present; a partial Contains line is not compliant.
Layer 2: the voluntary warning. "May contain traces of milk." "Made in a facility that also processes peanuts." "Processed on shared equipment with tree nuts." This is precautionary allergen labeling (PAL), and none of it is required by US law. The FDA does not mandate it, does not define the wording, and does not set a threshold for when it must appear. The agency's published position is essentially two-fold: advisory statements must be truthful and not misleading, and they cannot substitute for good manufacturing practices that control cross-contact in the first place.
One statement is law. The other is a courtesy. Once you see the label that way, a lot of confusing products start making sense.
"May contain" is not a risk ranking
A very common assumption - surveys of allergy consumers keep finding it - is that the phrasings form a ladder: "may contain" sounds scarier than "made in the same facility," which sounds scarier than nothing at all. Under US rules, there is no ladder. The wording is chosen at the manufacturer's discretion, and no US regulation assigns any risk level to any phrase.
The research backs this up in an uncomfortable way: published studies that tested products for actual allergen residue found that the specific PAL wording did not predict whether the allergen was really present. And the absence of any warning is not evidence of absence. In FDA sampling of dark chocolate bars, milk was detected in a large share of the products tested, including bars whose labels said nothing about milk and some carrying dairy-free-type claims.
So the honest reading of a precautionary line is narrow. It tells you the manufacturer chose to flag a possible cross-contact. It does not tell you how likely the contact is, how much allergen might be there, or whether that amount matters for your child. And a silent label tells you even less.
Cross-contact vs. cross-contamination: the word matters
You will see both terms online, and they are not interchangeable. The FDA and allergy organizations like FARE use cross-contact for allergens: the unintentional transfer of an allergenic food into another food, through shared equipment, shared lines, airborne flour, a shared fryer. Cross-contamination is the food-safety term for microbial hazards - bacteria and viruses getting where they shouldn't.
The distinction is not pedantry. Cooking to a safe temperature can kill bacteria, which is why cross-contamination has a fix. Cooking does not remove or neutralize allergenic proteins - milk protein that got into a product on a shared line is still milk protein after baking. Using "cross-contact" when you email a manufacturer or talk to a daycare kitchen also signals exactly what you are asking about, and tends to get you a more precise answer than the generic word.
The hidden names allergens hide behind
On a FALCPA-compliant US label, a major allergen cannot legally hide: if a product contains casein, the label must connect it to milk, either as "casein (milk)" or in a Contains line. So why learn the alternative names at all? Three reasons: labels are not always compliant (undeclared allergens are the leading cause of FDA food recalls), imported products may never have been through US labeling review, and unpackaged foods - bakery items, deli food, bulk bins, restaurant dishes - carry no FALCPA protection at all.
These are the alternative names worth recognizing on sight:
| Allergen | Names that mean it (or often do) | Worth knowing |
|---|---|---|
| Milk | casein, caseinate, whey, ghee, lactalbumin, lactoglobulin, curds | Ghee is clarified butter. "Non-dairy" creamers can still contain caseinate. |
| Egg | albumin (albumen), globulin, lysozyme, ovalbumin | Albumin is egg white protein; lysozyme appears in some imported foods. |
| Wheat | semolina, durum, spelt, farina, triticale, seitan | Semolina pasta and spelt bread are wheat, full stop. |
| Soy | soy lecithin, edamame, miso, tamari, textured vegetable protein (TVP) | Lecithin is often soy-derived; the source word matters, since sunflower lecithin also exists. |
| Sesame | tahini, benne / benne seed, gingelly (oil), sim sim | Tahini is ground sesame - central to hummus and halva. |
| Peanut | groundnut, arachis oil | "Groundnut oil" on imported labels is peanut oil. |
Imported products play by different rules
Everything above describes the US system. Precautionary labeling conventions vary widely by country, which matters the moment a product enters your house from an international grocery, a care package, or an overseas trip.
Foods imported for sale in the US are supposed to comply with FALCPA, but imported and specialty products are exactly where labeling gaps and undeclared-allergen recalls cluster - see our guide to baby food recalls for how to track those. Products bought abroad or shipped by relatives follow their home country's rules entirely: Australia and New Zealand have a standardized voluntary program (VITAL) with defined "may be present" wording, Japan uses its own shared-equipment phrasings (we cover them in the Japanese food labels guide), and some markets use no precautionary labeling conventions at all. On an imported package, the absence of a "may contain" line means even less than it does on a US one. Our foreign food labels guide covers the label-reading side in depth.
How to think about "may contain" without a medical ruling
No article, label, or app can tell you whether a "may contain" product is safe for your specific child. That depends on your child's allergen, reaction history, and your allergist's read - which is exactly why the most useful thing you can do with PAL confusion is turn it into questions for the person qualified to answer them:
- "Given my child's allergen and reaction history, how do you want us to handle 'may contain' products?"
- "Are there food categories where you consider cross-contact risk higher for us - chocolate, baked goods, granola, bulk foods?"
- "Should we treat 'shared facility' and 'shared equipment' wording differently, or the same?"
- "What about products with no precautionary statement at all - does that change anything for us?"
Alongside that conversation, two habits cost nothing: read the full ingredient list every time you buy, not just the Contains line (formulations change without the front of the package changing), and re-read even familiar products, because a "safe" snack can quietly gain a new line at any reprint.
Where a scanner fits (and where it doesn't)
The AllerSee™ scanner built into Baby Ledger AI cross-checks ingredient lists against the allergen profile you build for your child, and it knows the alternative names - casein flags against a milk profile, albumin against an egg profile, tahini against a sesame profile. It reads labels in English plus Japanese, Chinese, Korean, German, and Cyrillic (the app interface is in English), which helps on exactly the imported products where hidden names are most likely to slip through.
Two honest limits. First, no scanner reliably interprets precautionary statements - ours included. What a "may contain" line means for your child is a judgment call between you and your allergist; the scanner flags what it reads rather than ruling a product safe, and false negatives are possible, so it never replaces reading the full label yourself. Second, when the product database has nothing, it gets more cautious instead of waving the product through - an empty record is a reason to look harder, not a green light. The safety layer (the allergen cross-check, barcode scan, and FDA recall check) is free and unlimited on every plan; AI photo scans and Saurus questions have daily caps because each call costs real money to run. See how the AllerSee scanner works →
Frequently asked questions
Is "may contain traces" safe for a baby with a confirmed allergy?
That is not a call a label, an article, or an app can make. Precautionary statements are voluntary and unregulated in the US, so identical wording can sit on a genuinely risky product and a barely-risky one. Bring the specific products you are wondering about to your child's allergist and ask how they want you to handle precautionary wording for your child's allergen and history.
Is "may contain milk" more serious than "made in a facility that also processes milk"?
Not under US rules. No regulation defines either phrase or ranks one above the other, and product-testing studies have found the wording does not predict whether the allergen is actually present. Treat them as the same signal: the manufacturer flagged possible cross-contact, details unknown.
Are companies required to warn about possible cross-contact?
No. Precautionary allergen labeling is entirely voluntary in the US. A label with no "may contain" line is not evidence the product is free of cross-contact - FDA sampling has found undeclared milk in dark chocolate bars that carried no warning at all.
What is the difference between cross-contact and cross-contamination?
Cross-contact is the allergen term: an allergenic food unintentionally getting into another food, via shared equipment, lines, or surfaces. Cross-contamination is the microbial term, for bacteria and viruses. The practical difference: cooking can kill bacteria, but it does not remove or neutralize allergenic proteins.
What are the hidden names for milk and egg on a label?
For milk: casein, caseinate, whey, ghee, lactalbumin, curds. For egg: albumin (albumen), globulin, lysozyme. On compliant US packages these must be tied to the plain word "milk" or "egg" in the ingredient list or a Contains statement, but imported, non-compliant, and unpackaged foods do not give you that safety net - which is why the names are worth knowing. If you are still working through first introductions, our allergen introduction guide covers that stage.
Does a "Contains" statement list every allergen in the product?
Only the nine US major allergens, and only when a manufacturer chooses that format (it is one of two compliant options; some labels use only in-list parenthetical declarations instead). Allergens outside the Big 9 - mustard, celery, mollusks like squid or clams - are not required to be called out at all in the US. If your child reacts to something beyond the Big 9, the full ingredient list is your only reliable layer.
Do imported foods follow US allergen labeling rules?
Products imported for sale in the US are required to comply with FALCPA, but undeclared allergens remain the leading cause of FDA food recalls, and imported items are a recurring source. Anything bought abroad or shipped from overseas follows its home country's rules, which may use different precautionary wording or none. See our Japanese labels guide and foreign labels guide for the specifics.