What is the difference between cow’s milk allergy and lactose intolerance?

Cow’s milk allergy (CMA) is caused by the immune system reacting to the protein found in cow’s milk and other dairy products. Lactose intolerance, however, is caused by a deficiency of the enzyme lactase.^4,5 The possibility of a CMPA diagnosis should not be dismissed if an infant or child appears to be thriving and growing well.

What is the difference between cow’s milk allergy and cow’s milk intolerance?

Cow’s milk allergy has now replaced the term cow’s milk intolerance, which was previously used as a term for “non-IgE mediated CMA”.¹⁴ The term “allergy” acknowledges the involvement of the immune system.¹⁶ CMA babies can react to even the smallest amount of cow’s milk protein; therefore, the term CMI should no longer be used.

Signs and symptoms of lactose intolerance vs cow’s milk allergy

Lactose intolerance & cow’s milk allergy are often difficult to diagnose in babies and young children as they both present with similar gastrointestinal symptoms (GI). These may include symptoms such as nausea, vomiting, abdominal discomfort, bloating, diarrhoea, blood or mucus in the stool or allergic colitis. They may also display failure to thrive (FTT) in infancy. In most cases, these GI symptoms are caused by an allergic reaction to cow’s milk protein, rather than lactose intolerance.¹⁰

CMA infants and children may also have a family history of atopy and display skin and respiratory symptoms, such as acute urticaria and/or angioedema, atopic eczema, congestion, cough, wheezing, shortness of breath.¹ Lactose intolerance does not display these types of symptoms, as it does not involve the immune system.^5,6,15 CMA usually appears during infancy, while lactose intolerance usually starts after 4-5 years of age.⁶

How common is cow’s milk allergy and lactose intolerance in infants?

CMA is one of the most common allergies seen in infants in Australia and New Zealand, with a prevalence of more than 2% (1/50) and usually develops within the first year of life.^2,5,15

Primary lactose intolerance does not usually manifest clinically before 5 years of age.² Lactose intolerance in young infants is typically secondary lactose intolerance, which is transient to an infection. It usually improves with resolution of the underlying condition, or as the patient recovers from gastroenteritis.³

How to diagnose CMA and lactose intolerance?

The cornerstone of CMA diagnosis is an allergy-focused history which includes the key questions that need to be addressed when milk allergy is suspected. An IgE-mediated allergic reaction to cow’s milk can be obvious as symptoms are usually rapid and occur shortly after consuming the cow’s milk allergen. Non-IgE mediated CMA can be more challenging as symptoms are usually delayed and occur two or more hours after consuming the cow’s milk allergen.

To confirm CMA diagnosis, you should take a medical history and trial exclusion of all cow’s milk protein from the maternal diet (and infant diet if mixed feeding) for a period of 2-4 weeks. Followed by re-introduction of the milk allergen and recurrence of symptoms to confirm a CMA diagnosis.¹³ If it is still unclear after re-introduction, urgently refer the patient to a specialist for proper clinical diagnosis.

For diagnosing lactose intolerance in infancy, stool tests (for reducing substances) as well as breath hydrogen tests are not helpful.²⁰ A clinical history of gastroenteritis or associated stool testing for infections may be useful. This is a guide only. You should not use this information to diagnose a health or medical condition or problem, or alter, commence, or delay any medical treatment.

Helpful tools for diagnosing CMA and LI

Treatment timelines and options may vary depending on your patient’s age and the severity of their symptoms. Understand more about your patient’s treatment pathway by using our helpful Diagnostic and Treatment Algorithms.

References