Lactose Intolerance vs. Dairy Allergy: What’s the Difference?

Chrissy Carroll, MPH, RD| View Author Bio

When it comes to medical conditions, there is a lot of confusion about the difference between lactose intolerance vs. dairy allergies. It’s important to recognize that these are two very different conditions.   

Lactose intolerance is a digestive condition related to the sugar in dairy foods that can cause mild gastrointestinal symptoms. A dairy or milk allergy is an immune response to the protein in dairy products that can cause life-threatening symptoms.   

By learning about the differences between these conditions, it will help you better understand whether it’s safe to consume dairy products.

This post was written and reviewed for accuracy by Chrissy Carroll, MPH, Registered Dietitian (RD). This post is for informational purposes only and does not constitute medical advice. Always speak to a doctor regarding any medical concerns or questions. 

What is lactose intolerance? 

Lactose intolerance is a group of digestive symptoms that occur when your body cannot properly break down lactose, the sugar found in dairy products. 

When people have lactose intolerance, their body does not produce enough of an enzyme called lactase. This is the enzyme that breaks lactose down into its two individual sugars (called galactose and glucose) that the body can easily absorb.   

When the lactase enzyme is not present in the correct amount, the body does not fully break down the lactose sugar. This undigested lactose moves to the large intestine where it can cause uncomfortable symptoms like bloating, cramping, gas, or diarrhea. 

Good news, though: While uncomfortable, lactose intolerance is not a life-threatening condition. 

Here are some common questions that often arise when it comes to lactose intolerance: 

Is lactose intolerance an allergy? 

No, lactose intolerance is not an allergy. Instead, it is an issue of not properly digesting the sugar in certain dairy products. 

Is lactose intolerance genetic? 

Lactose intolerance has both genetic and non-genetic causes. Most commonly, it is thought to be the result of a genetic trait that decreases lactase production and activity over time (called primary lactose intolerance). 

This genetic trait is one of the reasons there are different rates of lactose intolerance among different ethnic backgrounds. For example, people of Asian and African descent may have higher rates of lactose intolerance, while those of Northern European descent are less likely to experience lactose intolerance.   

There is also a less common condition called secondary lactose intolerance, which is not related to genetics.  It occurs as a result of another medical condition.   

For example, when someone is suffering from gut inflammation due to an illness, the body may temporarily have reduced lactase activity. When the initial condition is addressed, this form of lactose intolerance usually goes away. 

Can children be lactose intolerant? 

Most infants are born with the ability to properly digest lactose, as that is the primary sugar found in breast milk. As such, it’s quite uncommon (though not impossible) for babies and toddlers to have lactose intolerance. 

Many older children and adults go on throughout life with the same level of lactase activity. However, some may experience decreased levels of lactase production. 

If you think your child does have lactose intolerance, be sure to talk to your pediatrician. Dairy products provide key nutrients for growing bodies, like calcium and protein, so it’s important to discuss any concerns with your doctor. 

How many people are lactose intolerant? 

In the United States, estimates of lactose intolerance range from around 9% to 36% of individuals. These rates vary widely though, due to the genetic variants mentioned previously along with challenges in estimating prevalence. For example, some people may have lower lactase activity but not experience symptoms while consuming moderate portions of dairy. Others may self-diagnose lactose intolerance but truly have symptoms related to another medical condition.

How do I know if I’m lactose intolerant? 

If you notice digestive symptoms after consuming large portions of dairy, that may be a sign that you could be lactose intolerant. Talk to your doctor about your symptoms. They may recommend a hydrogen breath test to confirm or rule out the diagnosis. 

In this test, you’re given a specific dose of lactose sugar. When that lactose is not broken down properly, your gut bacteria starts to ferment it, which produces hydrogen as a byproduct. This can be measured in the breath and used to diagnose lactose intolerance. 

Keep in mind that this test relies on the proper functioning of gut bacteria; situations like recent antibiotic use may affect results. 

Can you still eat dairy with lactose intolerance? 

Yes! There are many ways of continuing to enjoy dairy without risking symptoms.   

Because dairy supplies key nutrients like calcium and protein, it’s valuable to keep these foods in your diet or your child’s diet to support bone health. For example, study in Pediatrics found when adolescent females self-restrict milk due to a perceived intolerance, they took in less calcium per day and had lower spinal bone mineral content. 

But research has shown that most people with lactose intolerance can tolerate up to 12 grams of lactose without symptoms. This is the amount in about 1 cup of milk. 

Individual responses may vary, of course. If you have lactose intolerance and notice symptoms when drinking milk, rest assured that there are plenty of other dairy products that are lower in lactose and well tolerated.   

These include: 

  • Hard cheeses – This includes cheeses like cheddar, parmesan, and swiss. When cheese is made, the curd is separated from the whey (where most of the lactose is found). The minimal lactose left in the curd breaks down considerably as the cheese ages.
  • Lactose-free dairy products – Some dairy products are pre-treated with lactase to break down the sugar in the product. This allows for comfortable consumption by those with lactose intolerance. 
  • Yogurt – Though yogurt may have moderate levels of lactose, many individuals with lactose intolerance are able to tolerate it. The live cultures in yogurt may help break down some of the lactosemaking it easier to digest. 
  • Heavy cream – Don’t worry about a splash of heavy cream in your morning coffee or stirred into your tomato cream sauce. This high-fat dairy product is low in lactose. 
  • Butter – This dairy product contains extremely low levels of lactose. Feel free to spread it on your morning toast!
  • Find other delicious dairy recipes suitable for lactose intolerance in our recipe booklet. 

In addition, research suggests that consuming lactose with meals (especially those which contain healthy fats) helps to slow entry of lactose into the small intestine over time. This can cause fewer symptoms.   

What are dairy allergies? 

Unlike lactose intolerance, dairy allergies are a more serious condition that requires avoidance of dairy products. Dairy allergies occur when the immune system mounts a response to the proteins found in dairy products.   

This condition is not as common as lactose intolerance, though. It’s estimated that only 2% to 7.5% of the population worldwide suffers from any type of cow’s milk allergy. Even more reassuring is that many may outgrow their allergy over time. 

While we used to think there was only one type of dairy allergy, we now know there are a few different types – grouped into IgE-mediated allergies and non-IgE mediated allergies. 

What are IgE-mediated dairy allergies? 

This is the most common type of milk allergy. When a person with this condition ingests the protein in dairy products, the body produces IgE antibodies to attack the proteins. As part of this process, your body produces histamine and other chemicals that cause serious symptoms. 

Symptoms include the following, which generally occur within minutes to an hour of eating the food: 

  • Hives 
  • Wheezing 
  • Vomiting 
  • Tingling around the mouth
  • Anaphylaxis (a life-threatening reaction that can cause airway swelling, a drop in blood pressure, and shock) 

These are serious symptoms that should be evaluated by a medical professional immediately. 

How do I know if I have an IgE-mediated dairy allergy? 

If you think you or your child has a dairy allergy, be sure to talk to a doctor right away. Because symptoms of allergies can get worse with each exposure, it’s important to find out if an allergy exists and if the food should continue to be avoided. 

Testing for dairy allergies can be done with skin prick tests or blood tests: 

  • Skin prick tests:  A drop of the allergen is applied to the skin, typically on the back or arm. A very small disposable needle is used to then prick the skin so that the allergen enters the skin. After a little bit of time, the doctor will look at your skin to see if you have developed any hives. If you had a skin prick test for a milk allergen and developed a hive, it is likely you are allergic to milk.
  • Blood tests:  A vial of your blood will be collected and sent to a laboratory for examination. The lab can measure the IgE antibodies in the blood that are produced in response to certain food proteins. A high level of IgE antibodies in response to milk proteins would be a sign that you may have a milk allergy. 

A dairy allergy diagnosis can feel scary and overwhelming. Rest assured, with a little time and planning, you’ll find ways to handle this diagnosis and follow a dairy-free diet. 

It may help to know, though, that many children outgrow their allergies. Research in The Journal of allergy and clinical immunology found that about 79% of children with a milk allergy outgrew it by the age of 16. 

What are non-IgE-mediated allergies? 

Perhaps the most confusing in the world of dairy issues is the emergence of non-IgE-mediated food allergies, typically diagnosed in infants and young children. Non-IgE-mediated allergies still involve an immunologic response to the milk protein. However, unlike the traditional allergies described above, they do not involve the production of IgE antibodies. 

There are two common types of non-IgE-mediated dairy allergies: 

1) Food protein-induced allergic proctocolitis (FPIAP) 

This condition is typically diagnosed in infancy.  Many parents may not know this as the scientific term above; it is colloquially referred to by different names like “cow’s milk protein intolerance” or “cow’s milk protein allergy.” 

When a child with FPIAP ingests dairy proteins (through their mother’s breast milk or formula), they have a delayed immune reaction that affects their gut, causing blood and mucous in their stool. Infants may be fussy as well. 

Luckily, most children with this condition outgrow it – many by the age of 1, as noted by researchers in the Journal of allergy and clinical immunology.   

2) Food protein-induced enterocolitis syndrome (FPIES) 

FPIES is another condition that typically occurs in infants or young children. A few hours after the child ingests a certain trigger food, they typically develop severe frequent vomiting, followed later by diarrhea. They may also have symptoms like low blood pressure and lethargy.  

For children with FPIES, milk is one of the more common trigger foods. 

Luckily, like other dairy allergies, FPIES often resolves over time. According to research, most children outgrow it by 1 to 5 years of age. 

How do I know if my child has a non-IgE-mediated dairy allergy? 

Discuss your concerns with your doctor. Unfortunately, unlike IgE-mediated allergies, there are no diagnostic tests for non-IgE-mediated allergies. Instead, the diagnosis is usually made by your doctor based on clinical history and testing an elimination diet. Sometimes, oral food challenges may be conducted. 

Can you still eat dairy with a milk allergy? 

Unfortunately, no. When any type of milk allergy exists, you must avoid dairy completely.   

This is essential in IgE-mediated allergies where dairy ingestion can prove to be life-threatening. Even in non-IgE-mediated allergies though, dairy should be avoided. This includes all overt sources of dairy (like milk and cheese) as well as that which may be unexpected in food, like whey or casein. 

If you are parenting a child with a milk allergy, though, remember that many children do outgrow these allergies by adolescence. Don’t try to reintroduce dairy products on your own without your doctor’s consent.  However, do periodically check in with the pediatrician or allergist about the status of the allergy.   

If your medical team believes the child may have outgrown the allergy, they may conduct another allergy test or may do an in-office trial with a dairy product. For children with less severe non-IgE mediated allergies, they may recommend trialing products at home. 

Always follow the advice of your medical team. 

Personal Insight 

As a registered dietitian, I am familiar with lactose intolerance and dairy allergies in the professional scope.  But I am also familiar with the differences from a personal perspective since my son had food protein-induced allergic proctocolitis. 

Within a few weeks of his birth (TMI warning!), we started noticing mucous in his diapers, along with some fussiness. A few times, there was some minor blood as well.   

After talking with our pediatrician, he suggested removing dairy from my diet since I was breastfeeding. My son’s symptoms improved, but not completely. After some additional elimination tests at the advice of our medical team, we pinpointed that dairy, soy, and eggs were all problem foods for his non-IgE-mediated allergy. 

After eliminating all three of these, my son’s symptoms improved significantly. His diapers looked more normal, and his demeanor improved! 

I cut those ingredients out of my diet for a year while nursing. When my son was 13 months, we gradually started reintroducing foods one at a time to see if there was any reaction. Luckily, there was not! 

I cannot tell you the joy I felt eating a bacon, egg, and cheese sandwich again. 😉   

And of course, the joy I felt knowing my son would be able to fully enjoy all the delicious dairy foods that are available to us. 

The Bottom Line:  Dairy Allergies vs. Lactose Intolerance 

A dairy allergy is an immune-mediated response to the protein in milk products, which may be further broken down by IgE-mediated responses and non-IgE-mediated responses. IgE-mediated allergies (and sometimes FPIES as wellcan be life threating. For all allergies, dairy products must be avoided completely during this time.   

However, many children with milk allergies outgrow them in childhood. Be sure to regularly check in with your doctor to discuss a possible outgrown allergy, and never attempt to reintroduce an allergenic food without your doctor’s advice.

Lactose intolerance, on the other hand, is a digestive disorder related to the inability to break down the sugar in milk. It can cause uncomfortable gastrointestinal symptoms when large amounts of high-lactose dairy products are consumed. 

Unlike allergies, though, dairy does not need to be fully eliminated with lactose intolerance.  Focusing on smaller portions of dairy throughout the day (as opposed to one large meal) or choosing lower-lactose dairy products allows people with lactose intolerance to fully enjoy many of their favorite milk products. 

References: 

FPIES Foundation.  What is FPIES? 2011.  

Matlik L, Savaiano D, McCabe G, VanLoan M, Blue CL, Boushey CJ. Perceived milk intolerance is related to bone mineral content in 10- to 13-year-old female adolescents. Pediatrics. 2007 Sep;120(3):e669-77.  

Mattar R, de Campos Mazo DF, Carrilho FJ. Lactose intolerance: diagnosis, genetic, and clinical factors.Clin Exp Gastroenterol2012;5:113-121.  

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & Facts for Lactose Intolerance. 2018. 

Nowak-Węgrzyn A, Katz Y, Mehr SS, Koletzko S. Non-IgE-mediated gastrointestinal food allergy. J Allergy Clin Immunol. 2015 May;135(5):1114-24.  

Ruffner MA, Spergel JM. Non-IgE-mediated food allergy syndromes. Ann Allergy Asthma Immunol. 2016;117(5):452-454.  

Skripak JM, Matsui EC, Mudd K, Wood RA. The natural history of IgE-mediated cow’s milk allergy. J Allergy Clin Immunol. 2007 Nov;120(5):1172-7.  

Szilagyi A, Ishayek N. Lactose Intolerance, Dairy Avoidance, and Treatment Options. Nutrients. 2018;10(12):1994. Published 2018 Dec 15.  

Walsh J, Meyer R, Shah N, Quekett J, Fox AT. Differentiating milk allergy (IgE and non-IgE mediated) from lactose intolerance: understanding the underlying mechanisms and presentations. Br J Gen Pract. 2016;66(649):e609-e611.  

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