Is It Lactose Intolerance or a Dairy Allergy? How to Tell the Difference

Have you noticed you don’t feel your best after you eat or drink dairy? You may be starting to wonder if you have an allergy you didn’t know about. While an allergy to dairy is possible, it’s more likely you have lactose intolerance. So how do you know which it is? We help you differentiate between lactose intolerance and a dairy allergy.

What is the difference between a milk allergy and lactose intolerance? 

Lactose intolerance is a disorder of the digestive system, while a milk allergy is a disorder of the immune system. In each case, your body reacts to milk. But they are different types of reactions, and they lead to different kinds of symptoms.

If you have lactose intolerance, it means your body has trouble breaking down or digesting  lactose — the natural sugar in dairy products. This leads to digestive symptoms like stomach cramping, gas, and bloating. Symptoms usually start within a few hours. 

Lactose intolerance is caused by a problem making or using lactase — the enzyme that breaks down lactose. Some people make less lactase as they age. Others make less lactose because of medical conditions that affect the intestine. 

A milk allergy means that your immune system is activated by exposure to dairy. If you have a milk allergy, your body reacts to the protein part of milk as if it were dangerous. Symptoms usually start within minutes of eating dairy. And those symptoms aren’t limited to the digestive tract. An allergic reaction can cause symptoms that affect your skin, lungs, heart, digestive tract, and more. 

The cause of a milk allergy is less clear. Researchers are still trying to understand why some people develop allergic reactions to certain foods. 

Milk allergy in babies and young children

There are actually two types of milk allergy — IgE-mediated and non-IgE-mediated. The names are a mouthful. Their names refer to the part of the immune system that’s reacting.

Most adults (and older children) who have a milk allergy have the IgE-mediated type. This allergy follows the pattern of  classic food allergy. An IgE-mediated reaction happens within minutes of milk consumption and include symptoms like hives, cough, or wheezing. This type of allergy tends to persist and can have life-threatening consequences.

Most babies (and younger children) who are allergic to milk have the non-IgE-mediated type. These reactions usually happen more slowly. They can happen hours or even days after drinking milk. Symptoms are often related to pain with digestion. This includes vomiting, diarrhea, and fussiness. Sometimes they can even have bloody stools. 

It’s common to confuse these symptoms with lactose intolerance. But lactose intolerance is rare in children younger than 5 years. And the good news is that children are much more likely to outgrow this type of milk allergy.

EXPERT PICKS: WHAT TO READ NEXT

• Home testing kits: Home testing kits for food allergies and sensitivities may not provide reliable results. 

• Allergy tests: There are a few different ways to test for food allergies. It’s best to do so with the guidance of an expert.

• Food sensitivities: Similar to lactose intolerance, food sensitivities have some important differences from food allergies.

Can you be allergic to milk without being allergic to lactose?

Technically, yes — you can be allergic to milk without being allergic to lactose. People with a milk allergy are sensitive to the protein part of milk, not the lactose. But most dairy products contain both milk proteins and lactose. So it’s hard to eat one without the other. That means people with a dairy allergy need to avoid foods that contain lactose. 

The tricky thing about milk allergies is that milk can be found in many foods that you may not think of as including milk. “Dairy” is the word used to describe all food products that are milk-based. This can include ice cream, yogurt, sour cream, butter, and cheese. 

How do the symptoms of lactose intolerance and dairy allergy compare?

Your symptoms can often help you determine if you have a dairy allergy or lactose intolerance. 

Symptoms of lactose intolerance usually start anywhere from 30 minutes to a few hours after eating dairy. They include: 

• Gas 

• Bloating

• Diarrhea

• Abdominal pain

• Nausea

Symptoms of a dairy allergy tend to show up more quickly after eating. They’re more likely to start within the first 30 minutes and include:  

• Hives

• Swelling or tingling of the mouth or lips

• Vomiting or diarrhea

• Scratchy throat, or feeling that the throat is closing

• Coughing or wheezing

• Lightheadedness

• Runny nose

Even though lactose intolerance can make you uncomfortable, reactions to dairy are not dangerous. Dairy allergy, on the other hand, can be life-threatening if you have a severe reaction. If you have symptoms that are affecting two body parts — like hives and wheezing — it’s considered anaphylaxis. This requires treatment with an epinephrine auto-injector (Epipen) and immediate medical attention.  

How do you diagnose a dairy allergy vs. lactose intolerance?

Diagnosing lactose intolerance doesn’t always require testing. If you think you might have lactose intolerance, discuss it with your primary care provider. They’ll ask you about your symptoms and what foods you usually eat. They might recommend that you avoid dairy foods to see if your symptoms resolve. If your symptoms go away when you avoid lactose, it’s more likely that you have lactose intolerance. 

If your healthcare professional needs more information, they may recommend one of the following tests to help diagnose a lactose intolerance: 

• Hydrogen breath test: You’ll drink liquid that contains lactose and then blow into a machine. A high amount of hydrogen in your breath means you aren’t absorbing lactose.

• Lactose tolerance test: This involves drinking a liquid that contains lactose, and then having your blood tested 1 and 2 hours later. If your blood sugar doesn’t go up, it means your body isn’t absorbing the milk sugar.

If your symptoms fit more with a possible dairy allergy, your healthcare professional may order one of the following allergy tests: 

• Skin testing: A tiny prick is made in the skin and then exposed to a small amount of the protein found in milk. If your skin develops redness and swelling, it’s a sign of dairy allergy. 

• Blood tests: A sample of your blood is drawn to measure the level of IgE antibody against milk. A high level usually means you’re allergic to milk. 

Your doctor or healthcare professional will help you understand what testing, if any, is right for you. 

What can you do about lactose intolerance or a dairy allergy?

If you’re experiencing any sort of discomfort after eating foods with milk or lactose, here’s what you can do. 

Lactose intolerance

If you think you have lactose intolerance, try the following:

• Keep a food diary. This can help you pay attention to patterns and see what foods seem to trigger your symptoms the most.

• Eat lower-lactose foods like cheese or yogurt. Hard cheeses have less lactose than soft cheeses, so you might tolerate those better. 

• Try dairy products that are lactose-free, like lactose-free milk. 

• Use lactase supplements like Lactaid. These pills are available over the counter and can help your body digest or break down milk products. So you can still enjoy small amounts of lactose-containing foods. 

Dairy allergy

If you think you have a dairy allergy, you should:

• Avoid all dairy products.

• Read food labels carefully. People with a dairy allergy can often react even to small amounts.

• Carry an epinephrine auto-injector (Epipen) at all times

• Follow up with your regular healthcare professional or an allergist.

Why trust our experts?

Written by:

Jill L. Jaimes, MD

Jill L. Jaimes, MD, is a board-certified pediatric emergency medicine physician with over 20 years of clinical experience. She received her medical degree from Baylor College of Medicine and completed her residency and fellowship training at Texas Children’s Hospital.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Karen Hovav, MD, FAAP

Karen Hovav, MD, FAAP, has more than 15 years of experience as an attending pediatrician in a variety of clinical settings. She has worked in a large academic center in an urban city, a small community hospital, a private practice, and an urgent care clinic.

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