Medically reviewed by Shahzadi Devje, Registered Dietitian (RD) & Certified Diabetes Educator (CDE)
Do you sometimes feel bloated and gassy after eating dairy? Do you have trouble digesting milk or other dairy products? You may be one of the millions of adults sensitive to dairy.
Dairy sensitivity can cause a wide range of symptoms, from stomach cramps to migraines. If you're experiencing any of these symptoms, it's important to figure out whether dairy might be the root cause.
- How do I know if I'm sensitive to dairy?
- Popular food sources of dairy
- Additional examples of foods and products that often contain milk
- What's the difference between dairy sensitivity and lactose intolerance?
- Causes beyond one's ethnic background
- Dairy allergy tests
- Lactose intolerance tests
- Dairy intolerance tests you can do at home
- What about milk from other animals?
- How can you safeguard yourself?
As a registered dietitian, I'll discuss the signs and symptoms of dairy sensitivity in adults and the difference between milk allergy and lactose intolerance. In addition, I'll share some tests you can explore to determine if dairy might be contributing to your issues.
How do I know if I'm sensitive to dairy?
While there's no one-size-fits-all answer to this question, there are some general signs and symptoms. The following are numerous dairy sensitivity symptoms to be on the lookout for:
- stomach pain or cramps
- bloating and gas
- diarrhea or constipation
- nausea or vomiting
- skin rash or hives
- itchy eyes
- runny nose
It's important to note that dairy sensitivity symptoms can be wide-ranging, and not everyone will experience the same ones. Plus, dairy sensitivity is often confused with lactose intolerance, so it's important to understand the difference between these conditions.
Popular food sources of dairy
Dairy products come from the milk of mammals. The most common sources of dairy are cow's milk, goat's milk, and sheep's milk.
Other milk products include:
- ice cream
- sour cream
- ghee and butter
- and yogurt
Additional examples of foods and products that often contain milk
It isn't always easy to tell if a food contains dairy. That's because dairy can be hidden in foods and products.
Here are some examples of foods and products that often contain milk:
- baked goods
- canned tuna fish
- deli meats
- hot dogs
- lunch meats
- sauces and soups
- coffee drinks and lattes
- high protein flours
- instant mashed potatoes
- frozen prepared meals
- waxes on some fruits and vegetables
What's the difference between dairy sensitivity and lactose intolerance?
Lactose intolerance is not the same as dairy sensitivity (interchanged with milk allergy or dairy hypersensitivity) in that it's not an immune reaction. In other words, lactose intolerance isn't an allergy.
However, both conditions can cause similar symptoms.
Lactose intolerance unfolds when you don't have enough of the enzyme lactase to break down lactose, a type of sugar found in dairy products. Undigested lactose ends up being food for the resident gut microbes. As they ferment the lactose, they create gases that cause bloating, flatulence, pain, and sometimes diarrhea.
Why is it that some folks can drink milk without any problems while others can't?
Well, it has to do with our genes. You see, the ability to produce lactase is something that's passed down from our parents. So, if your parents were lactose intolerant, chances are you will be too.
Let's dig into this a bit further.
Lactase production typically peaks during infancy and childhood when we consume large amounts of milk. However, for some people, lactase production starts to decline during adolescence and adulthood. Sometimes, this decrease in lactase production can lead to symptoms of lactose intolerance.
Generally speaking, nonhuman mammals lose the capacity to digest lactose as they mature.
In fact, some groups, such as those from South America, Asia, and Africa, are more prone to lactase deficiency. In comparison, people of northern European ancestry or northwestern India usually retain the ability to break down lactose into adulthood.
Lactase deficiency affects up to 15% of people with northern European ancestry, up to 80 percent of black and Latino individuals, and up to 100% of American Indians and Asians.
Dairy sensitivity (milk allergy)
Dairy sensitivity is an immune reaction to dairy proteins.
When a person with dairy sensitivity (milk allergy) eats dairy, their body produces antibodies to fight the dairy proteins. This can cause a wide range of symptoms, from itchy eyes and runny nose — to stomach pain and diarrhea.
Dairy sensitivity symptoms usually appear within minutes to hours after eating dairy. What's more, in severe cases, dairy sensitivities can cause anaphylaxis, a life-threatening reaction that requires immediate medical attention.
A dairy sensitivity or allergy is less common than lactose intolerance.
It is difficult to determine the exact prevalence of cow's milk allergy due to the lack of a precise criterion for diagnosis.
So what is it in milk that people are allergic to?
The two main dairy or milk proteins that people are allergic to are casein and whey, and people can be allergic to one or both of these proteins.
Casein protein (s1- and s2-caseins) and whey proteins (alpha-lactalbumin and beta-lactoglobulin) are the most common allergens.
Most folks with cow milk allergies are sensitive to both caseins and whey proteins, which trigger an immune response. Specifically, the two primary immune-mediated adverse food reactions are IgE-induced and non-IgE-induced (allergic reactions).
A non-IgE mechanism is most commonly responsible for cow's milk allergy.
IgE-induced reaction is when the body produces antibodies (IgE) in response to a particular food. This type of reaction is often immediate and can cause anaphylaxis. A non-IgE response is when the body has an immune reaction to food but does not generate antibodies (IgE). Instead, other components of the immune system are activated. The result is a delayed reaction - taking hours or days.
If you're unsure whether you have a dairy sensitivity, lactose intolerance, or milk allergy, it's important to see a doctor who can provide medical advice.
Causes beyond one's ethnic background
There are a few other things that can cause dairy sensitivity or intolerance. For example, certain medical conditions like coeliac disease and Crohn's disease. And, of course, you might develop lactose intolerance as you age, as we discussed earlier.
Apart from one’s ethnic background, other reasons can contribute to lactose intolerance. For instance, issues with the digestive system, such as inflammation (Crohn’s disease or celiac disease), can lead to reduced production of the enzyme. Certain antibiotics or a bout of infection can also interfere with one’s ability to produce the lactase enzyme.
Dairy allergy tests
There is no standard test for cow's milk allergy. As a result, the diagnosis isn't simple and is primarily based on the patient's history of symptoms and physical examination. Indeed, it's valuable to document the occurrence of dairy sensitivity symptoms and when they occur.
Despite the absence of a gold standard, there are some allergy tests that might offer some value. These include skin prick testing, an exclusion diet and a blood test.
Skin prick testing
The most common way to test for dairy allergy is the skin prick test. During this test, a small amount of dairy allergen is placed on the skin, and then a needle is used to prick the surface of the skin. If you're allergic to dairy, you'll typically develop a raised, itchy bump (similar to a mosquito bite) within 15 minutes or so.
Another way to test for dairy allergy is through a blood test. This test looks for the presence of dairy-specific antibodies in your blood. Nevertheless, this test is more expensive and not as widely available. Plus, it's not 100% accurate in diagnosing a cow's milk allergy.
One dairy allergy test is the exclusion diet, where dairy is completely removed from the diet for a period of time (usually two to four weeks). It's then slowly reintroduced to assess for symptoms.
Learn all about the importance of gut health and how you can improve it naturally in this comprehensive guide on gut healing foods?
Lactose intolerance tests
A few different tests can be used to diagnose lactose intolerance.
Hydrogen breath test
The most common test is the hydrogen breath test. This test measures the amount of hydrogen in your breath. Typically, very little hydrogen is detectable in your breath. But when you eat foods containing lactose, bacteria in your gut break down the lactose, producing hydrogen gas.
If you have lactose intolerance, you'll usually have high levels of hydrogen in your breath after consuming dairy.
Other tests for lactose intolerance include the stool acidity test and an exclusion diet.
Stool acidity test
The stool acidity test measures the amount of acid in your stool. When you have lactose intolerance, undigested lactose ferments in your gut and produces lactic acid and other short-chain fatty acids, leading to diarrhea.
Thus, if you have lactose intolerance, you'll usually have high levels of lactic acid and other short-chain fatty acids in your stool.
The stool acidity test is not as commonly used as the hydrogen breath test or the exclusion diet.
One of the most frequent tools to diagnose lactose intolerance is an exclusion diet. For example, a low-lactose diet is used for symptom relief. Then, lactose is reintroduced to evaluate symptom recurrence. It's been reported that symptoms typically improve within 48 hours of lactose exclusion.
Lactose tolerance test
The lactose tolerance test is the most compelling test for diagnosing lactose intolerance.
During this test, you'll drink a solution that contains high levels of lactose. Then, blood samples will be taken over the next two hours to measure your body's production of glucose.
If you have lactose intolerance, your body will have trouble digesting the lactose, and you'll have lower than normal levels of glucose in your blood. That's because your body cannot break down the lactose into glucose.
Dairy intolerance tests you can do at home
If you're interested in doing a dairy intolerance test at home, there are a few options.
MyAllergyTest is an FDA-approved home dairy intolerance test that you can order online. This test uses a finger-prick blood sample to measure your body's reaction to dairy proteins. The results of the MyAllergyTest are typically available within days.
It's important to note that at-home tests don't have the same accuracy as tests done by a healthcare professional.
At-home dairy intolerance tests measure the levels of dairy-specific antibodies in your blood. However, research indicates that these antibodies are not always a reliable marker for dairy intolerance.
At-home dairy intolerance tests are not always accurate and should not be used to diagnose dairy sensitivity. If you think you might be dairy sensitive, it's important to see an allergist or doctor who can rule out other conditions and confirm a diagnosis.
What about milk from other animals?
The proteins in cow's milk are comparable to those in goat, sheep, and other ruminant milk. As a result, if you're allergic to cow's milk, you will likely have a negative response to other types of milk.
Before consuming goat, sheep, or other ruminant milk, be sure to check with your allergist.
How can you safeguard yourself?
If you're dairy sensitive, it's important to know how to protect yourself. Here are some tips:
- Read food labels carefully. Look for dairy ingredients like whey, casein, and lactose.
- When in doubt, ask the waiter or chef about the ingredients in a dish.
- Bring your own dairy-free food to parties and potlucks.
- Be aware that dairy can be hidden in unexpected places, like medications, vitamins, and supplements. Always read the labels on these products.
Shahzadi is an award-winning registered dietitian (RD) regulated by the College of Dietitians of Ontario and a certified diabetes educator (CDE), approved by the Canadian Diabetes Educator Certification Board. A notorious foodie, she's dedicated to helping you end your cooking wars, transform your health, and be the best version of yourself! Shahzadi is an on-air nutrition expert for CTV Your Morning and a regular contributor to other national media outlets.