Cow’s milk allergy and lactose intolerance are not the same. 

Cow’s milk allergy and lactose intolerance are often confused with each other, but they are very different. If you suspect your baby may have an issue with dairy, it’s important to learn what sets them apart so you can have an informed conversation with your pediatrician.

What triggers CMA?

Cow’s milk is made up of lots of different components such as proteins (casein and whey), milk sugar (called lactose) and fat.

An allergic reaction happens when the immune system mistakes the proteins in cow’s milk as a threat, when in fact they should be harmless. The body then releases chemicals including histamines that trigger the signs and symptoms of an allergic reaction.

What triggers lactose intolerance?

lactose intolerance, the digestive system can’t fully digest this milk sugar, because it doesn’t make enough of the lactase enzyme. So instead of being digested and absorbed, the lactose travels intact to our large bowel to be used as fuel for our friendly gut bacteria. This can release gases that cause the symptoms of lactose intolerance.

Who has dairy issues?

Cow’s milk allergy tends to affect younger children under the age of 3 years. Most will grow out of this food allergy as they get older, often by the time they start school.

Only in very rare cases does lactose intolerance affect babies from birth (called congenital lactase deficiency). In this case, the person remains lactose intolerant for life.

What are the symptoms?

Cow’s milk allergy and lactose intolerance can share some of the same signs and symptoms, including feeding and bowel problems such as:

  • Gas
  • Diarrhea
  • Bloated tummy
  • Tummy aches and cramps
  • Tummy rumbling
  • Feeling sick

However, since cow’s milk allergy involves the immune system, babies who are allergic to cow’s milk protein may also show allergy symptoms like an itchy rash, wheezing, or runny noses and coughs. These aren’t seen in lactose intolerance, since that doesn’t involve the immune system.

Another difference is that with cow’s milk allergy, even a small amount of cow’s milk protein could give your baby an allergic reaction. With lactose intolerance, many people can eat small amounts of milk products without noticing any symptoms.

How are they diagnosed?

There are different tests for cow’s milk allergy and lactose intolerance, so it’s important to discuss your child’s symptoms in detail with their pediatrician, who will decide which tests are most appropriate.

If cow’s milk allergy is suspected, your doctor may request an allergy test such as a skin prick test or blood test, and/or advise you to put your baby on an elimination diet followed by a food challenge.

If your doctor thinks it may be lactose intolerance, he or she may request a hydrogen breath test, lactose tolerance test, milk tolerance test or stool sample.

How are these conditions managed?

Since cow’s milk allergy and lactose intolerance are caused by two different problems, there are slightly different ways of managing each condition.

Cow’s milk allergy is managed by completely eliminating cow’s milk protein from your baby’s diet, as even a small amount of cow’s milk protein could potentially trigger an allergic reaction. Initially, lactose intolerance may be managed by completely eliminating cow’s milk protein from the diet, too. However, an entirely dairy-free diet is rarely needed in the long term. Most people with lactose intolerance are able to digest some lactose, as they still have a low level of the enzyme, lactase. Some dairy products can be carefully reintroduced into the diet – how much depends on the individual, so it’s important to follow the guidance of a dietitian when doing this. Some babies may benefit from having a lactose-free infant formula.

In either case, it’s important that you don’t make any changes to your child’s diet without the supervision of a healthcare professional. Be sure to speak to your doctor if you’re concerned that your infant might have cow’s milk allergy or lactose intolerance.