Detecting Milk In The Foods You Buy

In the past, it was somewhat more difficult to figure out whether a food contains milk products or not. The Food and Drug Administration now now requires that manufacturers list any of the 8 most common food allergens (milk, egg, soy, wheat, fish, shellfish, peanut, and nut) in their ingredients list, or at the end of their ingredients list because of The Food Allergen Labeling and Consumer Protection Act (FALCPA), which took effect in 2006.
Because of FALCPA, you should be able to read an ingredient list to find out if something contains milk. It will state CONTAINS MILK at the end of an ingredients list, or the word MILK will be written in parentheses after a dairy ingredient. For example, an allergen warning might look like this:

Ingredients: Wheat flour, sugar, oats, eggs, butter (from milk), baking soda.

Or, like this:

Ingredients: Wheat Flour, sugar, oats, eggs, butter, baking soda.
CONTAINS MILK.

Unfortunately, FALCPA does not state how manufacturers should label potentially contaminated products. It is up to the manufacturer to voluntarily print warnings of cross contamination on labels that state "manufactured on equipment shared with milk" or "manufactured in a facility that processes milk products" or "may contain traces of milk". It is up to the consumer (and his or her allergist) to assess whether a product is safe to consume.
In general, if a product claims to be "manufactured on shared equipment" with milk, I assume it has milk in it and don't offer it to my severely milk-allergic child.