Infants with Milk Allergy

January 10, 2014 Uma Pisharody, MD, FAAP


A 4 week-old infant and his mother came to my office last week.  The mother had started seeing small flecks of blood and stringy mucous in the infant’s diapers a week prior.  The baby was fine in every other way, breast feeding normally, and looked quite healthy when I examined him.

I diagnosed the infant as having cow’s milk protein-induced proctocolitis, the term referring to allergic inflammation of the lower gastrointestinal tract from exposure to cow’s milk. 

This is a diagnosis I make often. Here's what you should know about infants with milk allergies:

  1. It’s more common than you think. 2-3% of infants in the U.S. are allergic to cow’s milk protein. It is even more common in infants with eczema or who have parents or siblings with allergies.
  2. It’s seen in breast fed babies.  Over 50% of infants with this condition are breast milk-fed infants.  But remember, the babies are allergic to the dairy in their moms’ diets, not to their mothers’ breast milk per se!
  3. Switching to soy or goat’s milk doesn’t work.  Over two-thirds of infants with cow’s milk protein allergy “cross-react” to soy protein (which means that they may not be truly allergic to soy protein, but their immune systems are just too “immature” to know the difference between the two).  Similarly, if a mother switches from drinking cow’s milk to goat’s milk, it won’t help, because the source is still a “different species”; the infant’s immune system will still respond to the “foreign” protein.
  4. Treatment takes time. The inflammation resolves when all traces of cow’s milk (and soy), are  removed from the infant’s diet.  In the case of formula-fed infants, we switch to special hypoallergenic formulas.  Typically after a successful switch, the bleeding stops within a week.  However, with breast fed infants, the improvement can be a little slower.  Since it can take up to 2 weeks for the dairy in a mother’s diet to circulate into her breast milk, the full effects may not been seen for up to a couple weeks.
  5. Allergy testing is not recommended.  The type of allergy that causes infant proctocolitis is not caused by the same allergic pathways which lead to more typical food allergies, such as those that cause anaphylaxis or hives after eating peanuts or shellfish.  Thus, using these standard tests to diagnose an infant’s allergy often leads to inconclusive results.
  6. It’s not a life-long allergy.  Nearly all infants outgrow the allergy within the first year of life.  50% outgrow it by 7 months of age, 95% by 9-12 months of age. 

Finally, a word of caution:  not all infants react to cow’s milk protein in the same way.  Although the infant in my example was perfectly well except for small amounts of blood in his stool, some infants react much more severely with vomiting, diarrhea, rashes, and even poor weight gain.  Since it can be hard to tell whether an infant’s symptoms are from allergy or not, it’s always best to discuss your infant’s symptoms with his doctor first.

If your doctor diagnoses your infant with cow’s milk protein allergy, you may find these additional resources helpful:


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