What is Cow’s Milk Protein (CMP)?

There are two basic types of cow’s milk protein: casein (found in what curdles) and whey (found in what doesn’t’ curdle). Babies with CMP allergy might be allergic to one or both of these types of proteins.1

What Causes Cow’s Milk Protein Allergy?

Like other allergic reactions, a cow’s milk protein allergy is caused by an immune system reaction to the proteins found in cow’s milk, dairy products made from cow’s milk, and even products that use cow’s milk protein ingredients like casein. The immune system proteins in cow’s milk as a harmful invader, triggering the release of histamine.1

The Difference Between CMP Allergy and Lactose Intolerance

Understanding the difference between a food allergy and a food intolerance can help you understand whether or not your infant is experiencing a cow’s milk protein allergy or lactose intolerance.

Lactose intolerance is an inability to digest or absorb lactose, a sugar, but it’s not an allergic reaction to protein or any other component of cow’s milk.2 Lactase is the enzyme responsible for digesting lactose and deficiency in this enzyme causes lactose intolerance. Although it's rare for babies to be born with lactase deficiency, lactose intolerance can happen as a result of other conditions which is called secondary lactose intolerance.

For help decoding the difference, look to the symptoms—if there are symptoms beyond gastrointestinal issues, it’s likely an allergy.

Symptoms of lactose intolerance include:3

  • Gas

  • Bloating

  • Stomach cramps

  • Nausea

  • Diarrhea

Symptoms of cow’s milk protein allergy may include any of the above, plus:1,3

  • Itching around mouth or throat

  • Swelling of and around the mouth and face

  • Wheezing or coughing

  • Shortness of breath

  • Hives

  • Runny nose

  • Watery eyes

  • Colic

Anaphylaxis is a clear and alarming sign that your little one has an allergy rather than an intolerance. If your baby has difficulty breathing or experiences shock, call emergency or head to the emergency department immediately.

Tests are on the menu if you see a potential allergic reaction to milk or formula. If you suspect your baby has cow’s milk protein allergy, talk to your doctor to better understand whether your baby is experiencing cow’s milk allergy or lactose intolerance and how to care for your little one. For more information about cow’s milk allergy, talk to your health care provider and explore our CMP allergy FAQs.

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