My friend Diana brought up a good question in the comments the other day, she was curious about the difference between lactose intolerance and casein intolerance. I thought that would be a perfect post, so here you go! Now there are a lot of facts, and this may not be 100% spot on, but you'll get the general idea and if you're curious to find out more, feel free to Google it!
Lactose is the sugar found in cows milk. People that experience symptoms after consuming dairy products (diarrhea, bloating, gas, etc.) may simply be lactose intolerant. This is when your body does not have the enzymes that are needed to break down the lactose sugar, and therefore you react to it. You might start by cutting out dairy until symptoms subside and then trying to re-introduce lactose free dairy products, or using a product like lactaid pills which help to break down the lactose sugars. Lactaid products are dairy products that do not contain the lactose sugar, even though they do come from cows. Also it should be noted that some all natural products like yogurt, sour cream, and hard cheeses are naturally lactose free and can often be tolerated.
Lactose intolerance can also show up when there are other food allergies or intolerance and sometimes when those other intolerances are dealt with, the lactose intolerance goes away. Wouldn't that be nice??
Casein is the protein found in cows milk. The symptoms are very similar to lactose intolerance but can also be more severe, some people even having anaphylactic reactions. Respiratory problems (coughing, wheezing, sneezing, runny nose) are also an issue here. The symptoms are also very similar to those of Celiac Disease or gluten intolerance. If you are casein intolerant you must avoid all dairy products, including many additives that are in many processed foods. For a better idea of what this means, check out this link. Note that even products that are labeled "non-dairy" may in fact contain casein, know your products!
What about goats milk? Well, goats milk does contain both casein and lactose, however the structure of these are different than in cows milk and may or may not be tolerated well by those with lactose or casein intolerance. Safer alternatives to cows and goats milk would include rice milk, soy milk, hemp milk, coconut milk and I'm sure there are others I don't even know about yet.
The most important thing is to read all your labels, even if the allergy list doesn't include milk, be safe and read through the ingredients anyway. Know the names of additives that milk hides under. Your best bet - eat as close to nature as possible. Avoid the foods with all the additives! But you already know that. I hope this has been helpful, I still have more to learn on this subject but this is an excellent start.