A Parent’s Guide to the Katz Study on Cow’s Milk Allergy – Ready, Set, Food!
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A Parent’s Guide to the Katz Study on Cow’s Milk Allergy

We break down findings from the Katz study on milk allergies for parents, including how early cow’s milk introduction helps reduce babies’ food allergy risk, and how babies with cow’s milk allergy don’t usually have soy allergies.

A study published in 2010 and led by Dr. Yitzhak Katz gathered data on risk factors for cow's milk allergies in babies, and how common cow’s milk allergies are in babies. The study involved a large cohort of babies from a single medical center, to get as accurate a picture as possible of cow’s milk allergy prevalence. In this article, you’ll learn how this study’s findings, including:

  • Regularly giving your baby cow's milk as early as possible can help reduce milk allergy risk.
    • As early as possible: babies who weren't exposed to milk early enough were at highest risk of developing a milk allergy
  • If you breastfeed, introducing cow's milk as a supplement to breastfeeding may help your child avoid a food allergy
  • Babies with milk allergies will usually show symptoms soon after they consume cow's milk.

One of the study’s goals was to find out if early introduction of milk reduced milk allergy risk, and if so, what age of introduction seemed most protective. We break down everything parents need to know about the Katz study, including what it means for your family.

Learn more about cow’s milk allergy from Food Allergy Research & Education (FARE): 

The Katz Study on Milk Allergies: Overview of the Findings 

What was the goal of the study?

To answer these main questions:

  • How common is cow's milk allergy?
  • What are the risk factors for IgE-mediated cow's milk allergy?
  • Does early introduction of cow's milk reduce the risk of cow's milk allergy?
  • How common is it for babies to have both milk and soy allergies?
What type of cow’s milk allergies did the study track?

IgE-mediated cow’s milk allergies (IgE-CMA), or “traditional” milk allergies.

These allergies usually cause the immune system to react seconds to minutes after a child consumes cow’s milk (and almost always within 2 hours).

Who took part in the study?
  • 13,019 infants
  •  All born in the same two-year period
  • All from same medical center in Israel
How many babies had cow's milk allergies? How did doctors diagnose the allergies?
  • 66 (0.5%) were diagnosed with IgE-CMA
  • These babies had:
    •  A history of an immediate reaction to cow's milk
    •  A positive skin prick test 
    • A reaction to cow's milk during an oral food challenge (or a previous life-threatening milk allergy reaction)
  • Babies with probable adverse reactions to milk were given the milk skin prick test and oral food challenge.
    • A soy skin prick test was also used, to see which babies with IgE-CMA also had soy allergy.
How many babies didn’t have a cow’s milk allergy? How many were excluded from the results, and why?
  • 12,638 babies were not diagnosed with cow's milk allergy
  • 315 babies were excluded because parents complained about adverse effects from cow’s milk (but the babies didn't have a proven cow's milk allergy) or they avoided cow's milk completely
How was the study conducted?
  • Via phone interview (95.8%) or questionnaire (4.2%), to learn babies' feeding history and whether they had an adverse reaction to milk.
  • Researchers tracked when parents first introduced babies to cow’s milk
    • Recommended dose of cow's milk: 4g milk protein per week (two 2g doses per week)
    • Mothers were encouraged to continue breastfeeding.
  • Healthy infants were compared with babies who had IgE-CMA to determine cow’s milk allergy risk factors.
What did the study show about early introduction of cow's milk?
  • Infants who didn’t regularly consume cow's milk until 4-6 months of age were at the highest risk of IgE-CMA
  • Average age of IgE-CMA onset: 3.9 months
    • All babies with IgE-CMA showed allergic reaction symptoms within 7 days of consuming cow's milk.
    • 82.8%  showed symptoms within 24 hours of consuming cow's milk
    • Symptoms usually occurred 15-30 minutes after the baby consumed milk, on average.
Average age that babies with IgE-CMA first consumed cow's milk: 110 days (~3.7 months)
How common was it for babies to have both cow's milk and soy allergies?
  • None of the babies with IgE-CMA also had a soy allergy.
  • AAP previously advised against soy milk for babies with IgE-CMA because 10-14% of babies with CMA also had allergic reactions to soy
  • So, it’s less common for babies to have both IgE-CMA and soy allergy than previously believed.
What should parents take away from this study?
  • Regularly giving your baby cow's milk as early as possible is crucial for reducing milk allergy risk.
    • Prior to 4-6 months if possible: babies who weren't exposed to milk until 4-6 months were at highest risk.
  • IgE-CMA is less common than usually reported 
  • Early cow’s milk exposure while still breastfeeding might promote tolerance
  • Milk allergy symptoms usually occur 15-30 min. after baby consumes milk

 

The Katz Study's Results

Key results of the Katz study on cow's milk allergies showed:

  • Babies who weren’t exposed to cow’s milk until 4-6 months of age were at highest risk of developing a milk allergy (group III in the chart below). 
  • Babies exposed earlier than 4-6 months had a better chance of avoiding milk allergies. 
    •  “Almost half of the newborns were exposed to CMP in the first 2 weeks of life. The incidence of IgE-CMA among these infants was extremely low.”

  • The average age of IgE-CMA onset was 3.9 months (~118 days). Full results for age at CMA onset (in days) can be found below.

  • The average age that babies with IgE-CMA were first introduced to cow's milk was 110 days (~3.7 months). 
  • 82.8% of the babies with IgE-CMA showed symptoms within 24 hours of first consuming cow’s milk. 
  • None of the babies with milk allergies also had soy allergies. 

Life After the Katz Study on Milk Allergies: What Should Parents Take Away?

Here's what parents should take away from the Katz study:

Introduce cow's milk to your baby early and often to reduce their milk allergy risk.

  • Start introducing cow's milk prior to 4-6 months if possible. Babies who weren't exposed until 4-6 months were at highest risk for a milk allergy.
  • If you breastfeed, introducing cow's milk as a supplement to breastfeeding may help your child tolerate cow’s milk. Don’t stop breastfeeding to switch over to cow’s milk, as breastmilk is the best nutrition source for babies at this age.

Babies with milk allergies will usually show symptoms soon after they consume cow's milk.

  • On average, the babies in the Katz study who had milk allergies usually showed allergy symptoms 15-30 minutes after consuming milk

It's not very common for babies with milk allergies to also have soy allergies. 

  • So, it will usually be fine to give soy milk to a baby with IgE-CMA.
  • If your baby has digestive problems when they consume milk and soy, they may have a food intolerance (not a food allergy) to cow's milk and soy proteins, known as MSPI.

Based on study results, milk allergy itself seems much less common than usually reported. 

 

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About Jessica Huhn: Jessica Huhn is a content writer for Ready, Set, Food! 

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