Cows' milk allergy or lactose intolerance

Cows' milk allergy and lactose intolerance are often confused with each other because some of the gastrointestinal (gut) symptoms can appear similar, but they are not the same thing.

The following table is a summary of some of the differences between cows' milk allergy and lactose intolerance. For more details see cows' milk allergy and lactose intolerance.

If you think your baby has symptoms related to their infant formula, talk to your doctor. Making the correct diagnosis is important so your baby can be given the most suitable formula and so, if needed, you can avoid giving them some foods.

Cows' milk allergy (CMA) Lactose intolerance
  • Happens when your baby's immune system reacts to proteins in cows' milk. 
  • There are 2 main types of CMA:
    • IgE-mediated CMA
    • Non-IgE-mediated CMA.
  • Some babies may have a mixed allergic reaction.
  • Occurs when your body doesn’t produce enough of the enzyme lactase, which breaks down lactose in your gut.
Ages affected
  • Symptoms usually start during the first few months of life and generally get better before the age of 3 years.
Ages affected
  • Usually seen over 6 years of age.
  • Infants and young children can have temporary lactose intolerance, usually after a tummy infection (viral gastroenteritis). It can last for about 4 weeks before the gut recovers and starts to break down lactose again.
  • Symptoms differ depending on the type of allergic reaction.
  • IgE-mediated CMA symptoms usually involves skin (it turns red, itchy, has hives or swelling), tummy (such as vomiting, runny poos or tummy pain), breathing problems (such as runny nose, noisy breathing, cough or wheeze) or your baby gets pale and floppy.
  • Non-IgE-mediated CMA symptoms usually involve tummy symptoms such as vomiting, runny poos or tummy pain and blood in the poos. 
  • Lactose intolerance only causes tummy symptoms, such as runny poos, tummy pain, bloating and not usually blood in the poos.
  • Completely remove cows' milk, dairy products and any foods with cows' milk-containing ingredients from your baby's diet.
  • If your infant is formula fed, it's important to choose the correct type of formula.
  • There are 3 options for babies with CMA (the choice depends on your baby's age and the type of CMA they have): 
    • soy formula (not funded)
    • extensively hydrolysed formula
    • amino acid formula.
  • Note: A lactose-free formula is not suitable for babies with CMA.
  • Read more about infant formula for cows' milk allergy.
  • Infants with lactose intolerance need to minimise lactose in their diet rather than totally cut it out, as they are likely to tolerate small amounts of lactose.
  • Lactose-free formulas are suitable. A soy infant formula can be used in babies older than 6 months.
  • Read more about infant formula products.


  1. Managing cows’ milk protein allergy in infants BPAC, NZ, 2019
Credits: Health Navigator Editorial Team. Reviewed By: Dr Jan Sinclair, Paediatric Allergy and Clinical Immunology, Starship, Auckland Last reviewed: 21 May 2020