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

Some people can’t stomach cow’s milk — but not for the same reasons.

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Dairy products are prominent in American culture. The average American eats 32 pounds of ice cream annually, 33.7 pounds of cheese, and—get this—164.6 pounds of milk, according to the International Dairy Foods Association.

Despite the fact that Americans love pizza parties and ice cream cones, products made from cow’s milk aren’t for everyone. Both lactose intolerance and dairy allergies can make digesting cow’s milk difficult—or even dangerous. These two conditions are often considered synonymous when in fact they’re anything but. While both conditions require caution around dairy products, they differ in causes, symptoms, and treatment.

What Is Lactose Intolerance?

Most Americans are familiar with lactose intolerance, and that’s because it’s not a rarity: It affects about 36 percent of people in the United States, and 68 percent of the global population, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Lactose intolerance is a disorder of the digestive system. The problem occurs in the small intestine. If the person does not produce the lactase enzyme, their small intestine cannot properly digest the lactose—a sugar found in cow’s milk—and it passes undigested into the colon and causes symptoms.

Someone who is lactose intolerant may experience the following symptoms after consuming too much dairy:

  • Diarrhea

  • Stomach pain

  • Bloating

  • Nausea

  • And gas.

Symptoms of lactose intolerance vary by the individual. Some people may be able to tolerate more lactose than others, or they may be able to stomach some cow’s milk products (like yogurt) better than others (like ice cream). Symptoms often begin 30 minutes to two hours after consumption.

The milk from each species is specifically formulated for the offspring of that species. When humans began consuming cow’s milk, it required some amount of adapting to produce the lactase enzyme and digest it effectively.

Some demographic groups—such as those of Scandinavian ancestry—have adapted to tolerate cow’s milk more than others. Conversely, some demographic groups in the U.S. are more at-risk for lactose intolerance than others, including Asian Americans, African Americans, American Indians, and Hispanics, according to NIDDK. In fact, lactose intolerance affects 90 percent of Americans of East Asian descent, according to the U.S. National Library of Medicine.

Lactose intolerance can easily be confused with other digestive disorders, such as irritable bowel syndrome, which also causes sensitivity to dairy. Here are other reasons you may have frequent upset stomachs.

What Is a Dairy Allergy?

Having a dairy allergy is *not* the same as being lactose intolerant. While the latter is a digestive disorder, a dairy allergy is actually a disorder of the immune system.

As with other food allergies, the immune system mistakenly perceives dairy products as a “dangerous invader,” according to the American College of Allergy, Asthma, and Immunology (ACAAI). If any amount of dairy is consumed—even trace amounts—the immune system attacks and causes severe and even life-threatening symptoms.

Someone with a dairy allergy may experience the following symptoms after exposure to dairy:

  • Upset stomach

  • Hives

  • Vomiting

  • Blood in their stools

  • And anaphylaxis.

Anaphylaxis is rare, but can be life-threatening. When the immune system overreacts and releases too many chemicals, it puts the body into shock, according to ACAAI. During anaphylaxis, the person may have trouble breathing, swelling, tightness in the throat, hoarseness, low blood pressure, rapid heartbeat, and even cardiac arrest.

Although one of the eight most common food allergies, dairy allergies are less common than lactose intolerance. Dairy allergies affect 2 to 3 percent of children younger than three years old, according to ACAAI, and 80 percent are expected to outgrow the allergy by age 16.

Treating Lactose Intolerance and Dairy Allergies

If someone has a dairy allergy, avoiding any and all exposure to dairy is critical and mandatory. Even foods with small amounts of whey or casein—the two proteins found in cow’s milk—can cause allergic reactions. If any amount of dairy is consumed, the person may require an injection of epinephrine (using an EpiPen, for example).

On the other hand, someone with lactose intolerance may choose to continue eating dairy products. They may be able to tolerate small quantities of dairy in one sitting, or they might take lactase tablets that help the body break down the lactose. (These tablets work well for some people, but are unfortunately not effective for all people with lactose intolerance.)

Many Americans consider dairy products essential for good health, and the U.S. Department of Agriculture recommends three cups of cow’s milk daily for Americans above the age of 9. However, milk can safely be omitted, and the nutrients provided in milk products can all be obtained from other foods, according to the Academy of Nutrition and Dietetics. Here are bone-boosting foods you can find outside of the dairy aisle.