This is the most frustrating misconception I have to deal with in regards to my milk allergy. Coming in at a close second is when people assume I also cannot have eggs. Because eggs come from cows apparently.
I can't even count the number of times people have confused this, and actually had the nerve to say to me, "No, you're not allergic, you're lactose intolerant." or "They're the same thing." Not being able to properly digest lactose is completely different than an immune system overreaction that can potentially be fatal. No, I cannot have "just a little bit", there is no magical pill I can take before eating something, I can't even touch it without my skin instantly becoming red and swelling with hives.
This misunderstanding is very dangerous for people with a true milk allergy. Assuming it is lactose intolerance, people don't take it quite as seriously, since even the most severe symptoms only cause discomfort. They may not be as careful in regards to cross contamination when preparing food, they may not be prepared for a life threatening reaction, they may think a trace amount of cream or butter in a dish won't be enough to do anything, etc. So not only is it frustrating to hear comments like these, it's scary, especially coming from someone in the food industry who is preparing your food.
Food allergy - An overreaction of the immune system to a specific food protein. When the food protein is ingested, it can trigger an allergic reaction, ranging from mild symptoms (rashes, hives, itching, swelling etc.) to severe symptoms (skin reactions - hives and swelling and pale or flushed skin, constriction of airways, drop in blood pressure, neurological symptoms such as confusion and anxiety/feeling of doom, loss of consciousness, etc.) A food allergy can be potentially fatal.
Lactose intolerance - People who are lactose intolerant are missing the enzyme lactase, which breaks down lactose, a sugar found in milk and dairy products. Therefore, they are unable to digest these foods, and may experience symptoms such as nausea, cramps, gas, bloating, and diarrhea. Lactose intolerance can cause great discomfort, however it is not life threatening.
This is a popular misunderstanding! (Lactose intolerance vs milk allergy). Here's the scoop on what you need to know about milk allergy:http://www.kidswithfoodallergies.org/page/milk-allergy.aspx