There are several types of proteins in cow’s milk responsible for triggering milk allergies. Casein is the main protein, and is responsible for 80 percent of the protein in milk. Casein is found in the solid curd that forms when milk is allowed to separate and sour. Most of the other proteins are found in the whey, which is the watery remaining part. An individual can be allergic to proteins from either part, or to both.

Dairy proteins are found in many types of foods, making it important for people with a milk allergy to carefully check the ingredients of food products before they are consumed. All of these common ingredients may contain milk proteins (Note: This is not a complete list):

• Milk, including condensed milk, dry milk, evaporated milk, malted milk, milkfat, powdered milk and mild solids
• Butter, artificial butter, butter solids, butter fat, butter oil and buttermilk
• Brown sugar flavoring
• Calcium
• Caramel color or flavoring
• Casein, caseinate and rennet casein
• Cheese
• Cottage cheese
• Cream
• Curds
• Custard
• Ghee
• Half & half
• High protein flour
• Ice cream
• Lactalbumin, lactalbumin phosphate, lactoglobulin, lactulose
• Lactose
• Nougat
• Pudding
• Sour cream, sour cream solids, sour milk solids
• Whey
• Yogurt

Milk proteins can also be found in a number of unexpected places. People with a milk allergy should be careful when consuming the following:

• Chocolate
• Margarine
• Processed meats (e.g., bologna, pepperoni, salami, hot dogs, sausage)
• Bread and breaded foods (often fried)
• Soy cheeses
• Canned tuna fish
• Chicken broth
• Hydrolyzed vegetable protein
• Chewing gum

In addition, kosher foods (foods that are in accordance with Jewish dietary laws) that are labeled with the symbols “D” or “DE” should be avoided. The presence of a “D” on a food product’s package indicates that the product contains milk protein. The presence of the symbol “DE” indicates that the product was produced on equipment that is shared with dairy products. Kosher foods labeled “pareve”, “parev” or “parve” are considered milk-free in accordance with Jewish law. However, these markings do not guarantee that the product is safe to consume. Pareve foods can be up to 1.5 percent milk protein.

Some medicines use lactose as a filler. This does not necessarily mean these medicines are off–limits to a person with a milk allergy, since lactose is a sugar and not a protein. Still, there is some evidence that small amounts of some milk proteins can be found in lactose and may affect highly sensitive individuals with milk allergies.

The milk protein casein is used in some types of manufacturing and can be found in several kinds of latex glove. Skin contact with this latex is enough to trigger an allergic skin reaction in many individuals with a milk allergy.