Manufacturers are only required to list ingredients, not contaminants.
Since, by definition, contaminants are accidental and incidental, there is
no way for a manufacturer to be sure what might be present.  If the law
required naming possible contaminents, everything would be labeled, "may
contain traces of" just about everything to avoid the legal liability.
The problem is that, no matter what the manufacturing process, a business
takes its legal life in its hands if it labels something as suitable for
people with allergies because there are no standards for this claim.
Therefore, if anything goes wrong, they can be sued--even if their product
had nothing to do with the problem.  At best they can tell you to what
degree they isolate their production line.

For example, I'm designing completely separate lines for my products.  But
there's no way I can guarantee absolutely that there is no possibility of
contamination.  My ingredients are made elsewhere and are shipped with
other products.  Even separate runs with equipment dedicated to a single
product isn't enough to be sure that there isn't a problem at parts per
million or even parts per billion level.  And laboratory testing to that
level for all allergens for each batch is unaffordable.  As bad as it is
for a small company, it's even worse for a large one because they have deep
pockets and attract lawsuits.

Flavors and spices do not have to be identified individually because that
could give competitors too much advantage.  That's left to the discretion
of the manufacturer.  I'm not even sure if they are required to identify
natural versus artificial--since I'm not planning to put flavorings in my
mixes (just recipes so the consumer can choose suitable ingredients), I'm a
bit weak on this part of the law.

There are kosher numerous certifying agencies, each with its own symbol.
Since dairy products must be eaten separately from meat products,
identifying products that contain dairy or ingredients made from dairy, and
products made on equipment that touched dairy (likewise for meat) happens
to be important to kosher consumers.  Different certification organizations
identify the latter class in different ways.  This is especially true when
the processing is cold and/or dry.  When DE is designated (it is used by
only a few organizations) some kosher consumbers will consider the product
pareve (otherwise it would be D) but not to be eaten on meat dishes.
Remember that kosher laws are literally concerned with one part in sixty if
the contamination is accidental.  (Kosher certification has much tighter
standards because anything preventable is not an accident.)

Kosher certification won't do you any good for eggs, nuts, or fish which
are all pareve--and therefore no need to provide special identification for
the kosher consumer.  However, you can be sure that nothing from shellfish
is present.

Barbara