Dairy allergy or lactose intolerance? Here's the difference

Lactose intolerance and an allergy to dairy, especially to cow’s milk, are often confused. These two conditions sound similar when loosely described, but there are big differences.

In simple terms, lactose intolerance is caused by not having enough of the enzyme (called lactase) that the body needs to break down lactose (the sugar found in milk and other dairy products).

A dairy allergy, on the other hand, functions like any other allergy; in this case it's the body’s reaction to the protein in milk, which causes the immune system to work overtime in response to the dairy. It has nothing to do with the functioning of the digestive system, even though symptoms can include stomach troubles. It is also one of the most common food allergies in infants and young children.

"Lactose intolerance and milk allergy are very different entities," explains Dr Amy E Barto, a gastroenterologist at the Lahey Clinic in Burlington, Massachusetts. "Milk allergy usually shows up early in life. Lactose intolerance is more common, takes longer to develop, and can occur at any time of life."

What are the differences?

To better understand the differences between the two conditions, we broke both of them down:

Lactose intolerance

Cause: A lack of the enzyme responsible for digesting lactose.

Signs/symptoms: While these may vary in intensity from person to person, the main symptoms include watery, acidic diarrhoea, stomach cramps, bloating, flatulence and excessive stomach rumbling. Nausea and vomiting are less common.

Diagnosis: Lactose intolerance can be diagnosed by your doctor who will ask you questions about your symptoms. You might also be asked to eliminate dairy products for a short while to see whether your symptoms ease up. Your doctor might also run tests to see whether you digest dairy normally.

Treatment options: There is no treatment, but lactose intolerance can be well managed through diet. The main concern could be a lack of calcium as dairy products that are high in calcium are off limits, but optimum calcium intake can be obtained through other sources, such as leafy green vegetables, canned fish such as tuna, almonds and calcium-enriched cereals.

Dairy allergy

Cause: The body’s immune response to proteins in cow’s milk.

Signs/symptoms: The symptoms may include hives, wheezing, coughing, watery eyes, itching, nasal congestion, an upset stomach (mostly in infants) and sometimes vomiting. In some cases, a dairy allergy can cause deadly anaphylaxis.

Diagnosis: Your doctor will ask for a detailed history of your (or your child’s) symptoms, how long after you’ve eaten certain foods your symptoms appear, etc. Allergy tests, such as skin prick tests or blood tests, may be performed to see whether the patient responds to dairy. The patient may also be asked to eliminate dairy for a while to see if symptoms ease up.

Treatment: Many infants outgrow a dairy allergy. According to a recent observational study, most children who suffer from a dairy allergy as infants will outgrow it by the age of five. Adults need to talk to their doctor to rule out other allergies.

Avoidance of any milk products is the only way to manage a dairy allergy. You should still consult a doctor or allergist to determine which dairy products are the strongest triggers before eliminating all dairy products. You can also consult a nutritionist if you are concerned about your calcium intake.

If dairy doesn't sit well with you

After reading this, you should be able to pinpoint whether you have a dairy allergy or lactose intolerance. No matter how light or severe, it's important to discuss your symptoms with your doctor.  

Saint Luke's Health System in Kansas, USA, gives the following tips on how to manage lactose intolerance symptoms:

  • Choose lactose-free products which will still offer calcium. These are more readily available than in the past.
  • Choose dairy sources with active cultures, such as yoghurt, as these active cultures make lactose easier to digest.
  • Take lactase-enzyme tablets with dairy to help you digest lactose. 
  • Eat plenty of other calcium-rich foods.

Those with dairy allergies can do the following to manage their symptoms, according to the American College of Allergy, Asthma and Immunology (ACAAI):

  • Learn how to read labels as cow's milk can be a common hidden ingredient in many processed foods.
  • Ask restaurants whether a dish you want to order is prepared with butter.
  • Milk is easy to replace in baked goods and in dishes – read up on plant-based options and find what works best for you.
  • Talk to your doctor about soy-based alternatives if your infant suffers from a dairy allergy. 

Image credit: iStock

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