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Column originally published Jun 28, 2016

Cows Milk Protein Allergy

Question: Our baby is almost two-months-old. She was a great nurser since she was born. Around two weeks of age, she developed a rash on both cheeks and on her neck, and she was a bit spitty. The nurse practitioner said that she had lactose-intolerance, and suggested that I give her lactose-free formula instead of breastfeeding. There was no improvement at all. Two weeks ago, we saw our family doctor. She suggested that we give her hypo-allergenic formula. Within a week, the rash has improved. Can I still breastfeed her? I have been pumping and storing my breastmilk these last few weeks.


You have a very interesting problem: is it lactose intolerance or milk allergy? Can you still breastfeed her if she has allergy? Let me explain this to you.

All human and cows milk contain lactose. It consists of two sugars: glucose and galactose, combined together. In the intestine, we have an enzyme called lactase that can break down lactose into its component sugars before absorption. All babies are born with lactase in their intestine so that they can digest lactose in their mother’s milk; therefore, young babies don’t have lactose intolerance.

As we get older and drink less milk, our ability to digest lactose decreases. In some ethnic groups like Chinese, as many as 85% of adults lack lactase in their intestines. They have lactose intolerance and cannot drink cows milk or consume any dairy product.

If an infant or toddler has a serious bout of gastroenteritis, she can lose the enzyme temporarily from her intestine. As a result, she can continue to have diarrhea after the infection is over. In that situation, we sometimes use soy formula which does not contain lactose. Within days to weeks, the intestine does recover its ability to digest lactose.

It is interesting that after one week of hypo-allergenic formula, your daughter’s rash has improved. This shows that she has cows milk protein allergy; the cows milk protein came from the dairy that you took, and passed through your breast milk to her.

Cows milk protein allergy is not an uncommon problem in young infants. Most of the time, it shows up as a rash called eczema. It can also cause vomiting, diarrhea, bloody stool, and sometimes chest congestion. If the symptoms are mild, nothing needs to be done. However, in your situation, if you want to nurse her, you should stop drinking milk, stop eating cheese and yogurt. You may also need to read labels on processed food. Casein and whey, two of the proteins derived from cows milk, are often added to processed food.

It is not uncommon for healthcare professionals to make the mistake of blaming lactose intolerance as the cause of digestive problem. Lactose intolerance is common in adults, but not in young infants.

If you decide to stop breastfeeding, you may have to keep her on hypo-allergenic formula instead of regular cows milk formula. The protein in hypo-allergenic formula is partially digested to reduce allergic reaction. Most children outgrow cows milk protein allergy after about one year of age. When she reaches that age, you can try her on regular homogenized milk and see whether she has any reaction.

I hope this helps to explain what has been going on with your daughter, and gives you some guidance on what you can do in future.