| There are more dairy products hiding out there than you think. Sure, buttermilk, cottage cheese, and sour cream are fairly obvious examples. It's probably easy to figure out that half and half and yogurt are dairy too. But while attempting to determine what allergies I might have, I wasn't allowed to have any dairy products - and found them in a lot more places than I had expected. Vegans, the severely lactose-intolerant, and those with a true milk allergy should read all labels carefully while shopping.
Anything marked casein is a dairy product. This includes calcium caseinate and other caseinates. Ghee, a clarified butter used in preparing most Indian food, still contains the dairy elements. Whey is also a dairy product - a hydrolysate to be exact - even if it has been delactosed. Many people are lactose-intolerant, but anything beginning with lacto- is going to be a derivative of dairy: lactulose, lactalbumin, lactoglobulin. (It should be noted that while some lactic acid is a fermentation of milk sugars, most of the lactic acid added to foods is from other sources.) Rennet is a cheese product. Dried milk solids, condensed milk, and anything else with the word milk - you guessed it - is a dairy product.
These will turn up in the most unlikely of places. I took to shopping at my local Fresh Fields, a grocery store with a lot of organic, health-conscious, and vegetarian items. In with the frozen foods, I found "soy cheese pizza" - it didn't say dairy-free, but I figured soy cheese would be okay, right? Wrong. Calcium caseinate is often used to give texture to cheese made from soy. Non-dairy creamer and some whipped toppings (including Cool Whip) may also contain traces of milk products. Some birth-control pills contain lactose, as do some prescription and over-the-counter drugs. | 
