What Is a Milk Allergy?

When someone has a milk allergy, the body's immune system, which normally fights infections, overreacts to proteins in milk. If the person drinks or eats a product that contains milk, the body thinks these proteins are harmful invaders. The immune system responds by working very hard to fight off the invader. This causes an allergic reaction.

Milk is among the most common foods that cause allergic reactions. Some kids with a milk allergy outgrow it as they get older.

What Happens With a Milk Allergy?

People who are allergic to milk react to one or more of the proteins in it. Some people are allergic to casein (pronounced: KAY-seen) protein and some are allergic to whey (pronounced: WAY) protein. Some people are allergic to both casein and whey.

When a person with a milk allergy eats these proteins,  the body releases chemicals like histamine. The release of these chemicals can cause someone to have symptoms like:

• wheezing
• trouble breathing
• coughing
• hoarseness
• throat tightness
• belly pain
• vomiting
• diarrhea
• itchy, watery, or swollen eyes
• hives
• swelling
  
• a drop in blood pressure, causing lightheadedness or passing out

Allergic reactions to milk can vary. Sometimes the same person can react differently at different times. Some reactions to milk are mild and involve only one part of the body, like hives on the skin. But even when someone has had only a mild reaction in the past, the next reaction can be serious.

Milk allergies can cause a severe reaction called anaphylaxis. Anaphylaxis can begin with some of the same symptoms as a less severe reaction, but can quickly get worse. The person may have trouble breathing or pass out. More than one part of the body might be involved. If it isn't treated, anaphylaxis can be life-threatening.

Milk allergy is often confused with lactose intolerance because people can have some of the same symptoms, like belly pain or diarrhea. While lactose intolerance can upset someone’s digestive system, it can’t cause a life-threatening reaction the way that a milk allergy can.

How Is a Milk Allergy Diagnosed?

If you might have a milk allergy, your doctor probably will want you to see an allergist or allergy specialist for more testing. They will ask about things like how often you have the reaction, the time it takes between eating a particular food and the start of the symptoms, and whether any family members have allergies or conditions like eczema and asthma.

The allergy specialist may do a skin test on you. This involves placing tiny amounts of milk protein on your forearm or back, making a small scratch or prick on the skin, and waiting to see if a reddish, raised spot forms. If so, it may mean there is an allergy to milk.

You may need to stop taking some medicines (such as over-the-counter antihistamines) 5 to 7 days before the skin test because they can affect the results. Check with the allergist's office if you’re not sure about what medicines to stop or for how long.

An allergist also might do a blood test. A small blood sample will go to a lab for analysis. The lab checks the blood for IgE antibodies to specific foods. If you have enough IgE antibodies to milk in your blood, you’re likely allergic to it.

If the results of the skin and blood tests are still unclear, though, an allergist might do something called a food challenge. During this test, a person gets slowly increasing amounts of milk while the doctor watches for symptoms.

How Is an Allergic Reaction to Milk Treated?

If you have a milk allergy, always carry two epinephrine auto-injectors in case of a severe reaction. An epinephrine auto-injector is a prescription medicine that comes in a small, easy-to-carry container. It's easy to use. Your doctor will show you how. Always have two auto-injectors with you in case one doesn't work or you need a second dose.

The doctor can also give you an allergy action plan, which helps you prepare for, recognize, and treat an allergic reaction. Share the plan with anyone else who needs to know, such as relatives, school officials, and coaches. Also consider wearing a medical alert bracelet.

Every second counts in an allergic reaction. If you start having serious allergic symptoms, like trouble breathing or throat tightness, use the epinephrine auto-injector right away. Also use it right away if your symptoms involve two different parts of the body, like hives with vomiting. Then call 911 and have them take you to the emergency room. You need to be under medical supervision because even if the worst seems to have passed, a second wave of serious symptoms can happen.

What Can I Do to Stay Safe With a Milk Allergy?

If you have a milk allergy, you must not eat or drink any products that contain milk or milk proteins.

Avoiding milk involves more than just leaving cheese off your sandwich. Be sure to read food labels carefully and not eat anything that you're not sure about.

Milk and milk proteins can show up in unexpected places, such as processed lunchmeats, salad dressings, baked goods, chocolate, and crackers. Even foods that say “non-dairy” still may contain milk protein. 

One thing that might not show up on a label is cross-contamination risk. Cross-contamination happens when a food you are not allergic to comes in contact with a food you are allergic to. This can happen if a manufacturer uses the same equipment to grind lots of different foods, for example.

Some companies put statements on their labels about the risk of cross-contamination, like: "May contain milk," "Processed in a facility that also processes milk," or "Manufactured on equipment also used for milk." You'll want to avoid products that have these kinds of alerts. But companies are not required to put cross-contamination alerts on a food label. So it's best to contact the company to see if a product might have come in contact with milk. You may be able to get this information from a company website. If not, contact the company and ask.

Cross-contamination is also a risk when you dine out or eat at a friend’s house. Foods you're allergic to can get into your food when someone uses the same surfaces, utensils, or oil to prepare different foods.

When you're not at home, ask what's in a food you're thinking of eating. Find out how the food is cooked. Many people find it's best to bring safe food from home or eat at home before heading out. If friends you're visiting or eating with don't know about your allergy, tell them in plenty of time so they can prepare. Don't share a drink or eating utensils with friends if they're eating foods you're allergic to, and avoid tasting any of their food.

Getting used to living with a milk allergy can take some time. But by being careful with what you eat and always having two epinephrine auto-injectors with you in case of a reaction, you can stay safe with your allergy.