If a glass of milk or a slice of pizza causes swollen lips, hives, or other significant symptoms, you may have an allergy to casein, a protein in milk. Another milk protein associated with food allergies is whey. Some people are allergic to both casein and whey.
Most people with an allergy to milk have symptoms which appear when they are infants and outgrow them as they get older. However, some people do not outgrow these symptoms and continue to be allergic as adults. It is unusual to develop an allergy to milk proteins later in life. Lactose intolerance can appear later in life with symptoms including bloating, pain, gas, diarrhea or gastroesophageal reflux. Lactose intolerance is not an allergy but an intolerance, where individuals are unable to digest the sugar lactose in milk. But that inability does not result in potentially life threatening reactions. It is important to learn how to recognize and avoid potential allergens.
A casein allergy occurs when your body's immune system mistakenly thinks the protein is harmful and inappropriately produces allergic (IgE) antibodies for protection. The interaction between these antibodies and the specific protein triggers the release of body chemicals such as histamine that cause symptoms which may include:
The most serious reaction to milk allergy is called anaphylaxis. This is a potentially life threatening reaction that can occur rapidly. Allergy to foods (including casein in milk) is believed to be the leading cause of anaphylaxis outside the hospital setting. People who have asthma in addition to a serious food allergy to an item, such as casein, are at greater risk for worse outcomes if they suffer an exposure and develop an anaphylactic reaction.
Symptoms such as swelling inside your mouth, chest pain, hives or difficulty breathing within minutes of consuming a milk product may mean you are experiencing an anaphylactic reaction and need emergency medical attention.