Lactose Intolerance vs. Milk Allergy: How Are They Different?

Posted and filed under Health Awareness.

Lactose intolerance and milk allergy are two conditions in which patients experience adverse health effects upon consuming milk products. It’s, therefore, no surprise that they are often confused and mistakenly used interchangeably. Yet, the two have distinct characteristics, and understanding their unique impacts and how to maintain a healthy diet in spite of them is important for patients.

Key Differences

Lactose intolerance is the body’s inability to fully digest the sugar, or lactose, found in milk. It typically results from a deficiency of lactase, an enzyme in the small intestine that helps turn milk into glucose and galactose. Without lactase, the lactose moves into the colon, where normal bacteria interact with undigested lactose, producing a range of uncomfortable symptoms.

Milk allergy, on the other hand, is the same as any other food allergy. The protein in milk produces an allergic reaction, so people with the allergy are at risk of serious reactions upon consuming both milk itself and products containing it. While an allergy to cow’s milk is seen most commonly, reactions can also occur with milk from goats, sheep, buffalo, and other mammals.


Lactose intolerance can develop at any time in a person’s life and is more common than milk allergy. It tends to be more common in certain populations with up to 90% of African Americans experiencing its symptoms. The condition is also common in Asians and Native Americans and is often seen in elderly populations. Roughly 30-50 million Americans are believed to have lactose intolerance.

Within 30 minutes to two hours after having milk or dairy products, most people with lactose intolerance experience one or more of the following symptoms:

  • Stomach pain
  • Nausea
  • Diarrhea
  • Gas and bloating

Milk allergies, on the other hand, are commonly seen in children under the age of three, although they can develop at any age. Oftentimes, children outgrow the condition by age five. Symptoms vary from one person to the next and can occur within minutes or hours after drinking milk or eating milk products. Immediate symptoms include:

  • Vomiting
  • Coughing and shortness of breath
  • Swelling of the tongue, lips, or throat
  • Itching or tingling around the mouth
  • Wheezing
  • Hives

Later, symptoms such as a runny nose, watery eyes, abdominal cramps, and loose stool or diarrhea may occur. Milk is also the third-most common food to cause anaphylaxis, a life-threatening condition in which the airway becomes blocked. For this reason, avoiding milk products and carrying an epinephrine shot is critical for patients with the allergy.


Diagnostics are available for both lactose intolerance and milk allergies. Doctors often encourage patients to keep food diaries when symptoms such as those listed above arise. To help differentiate among the two conditions, food allergy testing and hydrogen breath tests can be used to diagnose milk allergy and lactose intolerance, respectively.

Patients with lactose intolerance may be able to tolerate small amounts of dairy, especially those which are lower in lactose, such as yogurt or hard cheese. People with milk allergies, on the other hand, must avoid dairy, which also encompasses the ingredients ghee, lactulose, lactalbumin, whey, and casein.

Luckily, there are many alternatives to dairy available today. Nut and soy milk are useful substitutions people with both milk allergies and lactose intolerance can enjoy. With that said, it’s important for patients to ensure they’re getting enough calcium. While doctors may recommend supplements on an as-needed basis, foods rich in calcium such as dark leafy greens and almonds can also be incorporated into the diet to maintain optimal nutrition.

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