Lactose intolerance or cow’s milk allergy?
Author: Kathy Beck, APD, Paediatric Allergy Dietitian
There is still confusion between lactose intolerance and cow’s milk allergy in the community which can lead to detrimental effects. For example, it is not uncommon for me to see babies with newly diagnosed non IgE mediated cow’s milk allergy who have tried lactose free infant formula thinking that it is cow’s milk free with no improvement.
Lactose intolerance and cow’s milk allergy are both conditions triggered by consuming cow’s milk but differ significantly in their causes, symptoms, and management.
Lactose intolerance results from an inability to digest lactose due to low levels of the enzyme lactase. This results in lactose being present in the large intestine causing symptoms such as bloating, gas, abdominal pain and diarrhoea (sometimes frothy).
Cow’s milk allergy occurs when the immune system reacts to protein in cow’s milk causing a wide range of allergic symptoms. These include hives, vomiting, wheezing, diarrhoea or anaphylaxis in IgE mediated cow’s milk allergy and irritability, vomiting, frequent loose stools often with blood and mucous in non IgE mediated cow’s milk allergy.
Key Differences
| Lactose Intolerance | Cow’s milk allergy | |
| Cause | Inability to digest lactose due to low levels of the enzyme lactase | Immune system reaction to proteins in cow’s milk (casein, whey) |
| Mechanism | Digestive problem (not an immune response) | Allergic reaction (immune-mediated, can be IgE or non-IgE) |
| Symptoms | Digestive symptoms: bloating, diarrhea, gas, stomach pain | Wide range of symptoms: hives, vomiting, wheezing, diarrhea, eczema, or anaphylaxis |
| Severity | Usually uncomfortable but not life-threatening | Can be life-threatening (anaphylaxis in IgE-mediated CMA) |
| Age | More common in older children and adults | Most common in infants and young children, often outgrown by age 5 |
| Diagnosis | Hydrogen breath test, lactose tolerance test, or symptom tracking | Skin prick test, blood tests for IgE antibodies, elimination diets, or oral food challenge |
| Management | Avoid lactose-containing foods or use lactase enzyme supplements | Strict avoidance of cow’s milk and products containing milk proteins. |
| Triggers | Lactose (carbohydrate or sugar found in milk) | Milk proteins (casein and whey) |
If you are concerned that you or your child has one of these conditions the best person to talk to is your GP or dietitian.
About the author
Kathy Beck is a South East Queensland based paediatric dietitian who specialises in food allergy. Kathy is an active member of the Dietitian’s Committee of the Australasian Society of Allergy and Clinical Immunology (ASCIA). Kathy has been a dietitian for over 30 years with the last 15 years working in paediatrics in various clinical settings in Australia and England.
