No - not (yet) a federal requirement. More a courtesy to their
customers. There are also no federal standards as to what these
labels mean, and whether they are "true" or just covering some
liability. (If a company says it has dairy, can someone with a dairy
allergy sue for a damaging reaction?)

We can only infer from what we read on these labels the meanings of
the warnings. They might mean that the food contains milk (which
would show up in the ingredients), contains an ingredient derived
from milk (often obvious, but not always), was manufactured on
equipment exposed to milk, manufactured in a plant that also produces
foods containing milk, ...

As with foods labeled "Kosher dairy" that contain no obvious milk
ingredient, we have been more careful. My son and I do eat many of
these, but we're careful the first few times to make sure we have our
meds nearby. I know, it's kind of a "dairy roulette" game, because
each batch of food labeled with possible milk ingredients/exposure
could have more or less "contamination." It's turned out to work for
both of us, save for a few cases where the contamination did result
in some minor symptoms. But with such limited diets, it's sometimes
worth taking a small risk. It all depends on the amount of allergen
and the level of sensitivity.

It's sort of a statistics game, where we expect those foods to have
much less of the allergen than, say, a piece of cheese or a few
tablespoons of milk.

That said, we do try to keep such exposures to a minimum. For
allergies, there is such a thing as a "sub-clinical response" - where
symptoms, e.g., inflammation, are increased, even though there are
not blatant symptoms. The less allergen you take in, the less likely
you are to have some complication due to the exposure. The more you
take in (or the more often), the more likely it might be that some
otherwise small allergen exposure can tip you over the edge, or the
more likely the inflammation is to result in some secondary
complication (sinus infection, ear infection, ...)

Mark

>I have noticed
>(here in the USA), though, that some labels have actually started listing at
>the bottom something like "Contains: wheat, dairy", or "Allergy warning: nuts,
>soy", and so on. Is there a government program that's going to
>require this? Or
>is this voluntary? Also, how trustworthy are these warning flags?