Kosher certification is a very complex system of labeling, originally created for spiritual purposes.  However, over the years many individuals have also found it to be a handy way of identifying foods for special diets.  Before we go on, I believe it is important to address an ongoing debate regarding the safety of Kosher and Kosher "Pareve" products for those with milk allergies.  Based on policies of the Orthodox Union, the world's super power of Kosher certification, those individuals with a severe milk allergy should not rely completely on Kosher certification when selecting foods.  A detailed explanation for our conclusion is stated on the Orthodox Union's website as follows:

"The trace nuts and dairy disclaimer that is now printed on many products is there to warn consumers that although there are no nuts or dairy in the ingredients of the product itself, there is a possibility of parts per millions floating in the air and ‘contaminating’ the product.

The ‘contamination’ would only affect consumers with extremely severe allergies who can detect even the most trace amounts of the substance that they are reacting to. A product that is labeled OU (and thereby certified kosher parve) is halachically (by Jewish Law) parve. The parts per million does not affect the status of a product, because parts per million are negligible and have no halachic significance.

As an example, a factory might produce dairy and parve products on two separate production lines. Nonetheless, air-born particles of milk or whey powder might float onto the parve production line. Though a person might suffer an allergic reaction, the product is still halachically parve.

Companies have been especially cautious in the past few years to publicize this information as the public’s knowledge of allergens has grown."

Fortunately, for most individuals who choose to cut dairy from their diet for religious, personal, social, or medical reasons, Kosher labeling can be a very useful tool.  Kosher certification is issued by a number of different organizations throughout the world.  For this reason, various organization-specific symbols are utilized to identify Kosher products.  For a quick scan of the symbols to watch for, check the Crash Course to International Kosher Symbols.  

If this list makes your head spin, just remember a few quick rules.   There are some Kosher symbols that help to quickly identify dairy ingredients in a pinch. A "D," or the word dairy, on a label next to a "K" or "U" symbol (usually found near the product name) indicates the presence of milk ingredients.  A "DE" on a label indicates that the product was produced on equipment shared with dairy products. If the Kosher symbol includes the word “Pareve”, "Parev", or “Parve”, then the food is considered both dairy and meat-free. 

For a sample of how Kosher symbols can be read, we will look at the most relevant examples from the Orthodox Union's decoder.  Their famous symbol is the :

• An "OU" symbol indicates a Kosher product, that contains neither dairy nor meat, nor any dairy or meat derivatives. It also verifies that the product was not made on equipment that is also used for making dairy products. Such products may also be referred to as Pareve, Parev, or Parve.  Vegetarians and vegans find this label very useful, but should note that this does not guarantee that the product is free of eggs or honey, so check the label.   
• An "OU-D" symbol indicates that the product contains a dairy ingredient or a dairy derivative, or that it was made on equipment also used for making dairy products. This is an important indication to both dairy free and Kosher consumers, as Kosher laws do not permit a dairy food to be eaten or cooked with meat, or with foods made with meat ingredients.
• An "OU-M" symbol or an "OU-Glatt" symbol indicates that the product is Kosher meat.  Although it is free of dairy, it is either meat, a product made with meat ingredients or a derivative of meat, or made on equipment also used for making meat products. 
• An ‘OU-F’ symbol indicates a Kosher product with fish ingredients.

For a more extensive list of their Kosher labels and other important information for Kosher consumers, go directly to the Orthodox Union's website.