Dairy’s Health Effects

Lactose Intolerance

Approximately 36% of Americans (including children) have lactose intolerance—meaning they cannot digest lactose, a sugar found in cow’s milk and other dairy products. Prevalence among children of color is even higher—as high as 95% for Asian kids.

This should not be a surprise. Milk is “designed” by nature as a growth agent for babies. Most species, including humans, are biologically programmed to outgrow milk after weaning.

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Symptoms of lactose intolerance

When a child with lactose intolerance consumes dairy, the symptoms can include abdominal distention, cramps, excessive flatulence, diarrhea, constipation, nausea, and vomiting. Not to mention headache, muscle pain, joint pain, oral ulcers, and even urinary symptoms. 

Symptoms typically occur 30 minutes to two hours after ingesting dairy. 

While the prevalence and severity of lactose intolerance are often under-appreciated, the sheer multiplicity of potential symptoms can easily prompt misdiagnosis.    

For pediatricians, gastroenterologists, and general practitioners who routinely screen for and manage the following GI conditions, it is worth asking whether lactose intolerance might be considered as the culprit, due to overlapping clinical symptoms:

  • Irritable bowel syndrome
  • Celiac disease
  • Tropical sprue
  • Cystic fibrosis
  • Inflammatory bowel disease
  • Diverticular disease
  • Intestinal Neoplasm or polyp
  • Excessive ingestion of laxatives
  • Viral gastroenteritis
  • Bacterial infection
  • Giardiasis
  • Gastrinoma

Our advisory team of physicians and nutritionists recommends a 30-day dairy abstinence program as a starting point. Remove all dairy from the child’s diet for 30 days and see if the symptoms abate.

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Dairy Allergy

It is important to distinguish between lactose intolerance and dairy allergy. A dairy allergy is an immune response to the proteins found in dairy. It can present as a wide variety of symptoms, ranging from mild and uncomfortable to severe and life-threatening. These symptoms include wheezing, rashes, lip-swelling, hives, diarrhea, acute asthma, iron deficiency, all the way up to (potentially fatal) anaphylaxis.
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A dairy allergy is an immunological reaction to the proteins in milk (casein and whey). When a child (or anyone) with a milk allergy consumes dairy of any kind, the body triggers an immune response to fight off what it sees as a harmful substance. Symptoms can range from very severe life-threatening anaphylaxis to less serious reactions such as hives. 

A dairy or milk allergy reaction can be immediate or occur up to three days after consuming dairy (delayed allergic reaction or non-IgE mediated reactions). These delayed responses make the allergy difficult to diagnose, as people may not associate their symptoms with the cow’s milk ice cream they ate three days prior. Patients with delayed allergic reactions often have ‘thick note syndrome’; i.e., long medical history files that no doctor has been able to solve.

The symptoms triggered by dairy allergy may often look like disease and can seem elusive given their delayed response. The unifying mechanism underlying all these symptoms is inflammation. A dairy (or other food) allergy can lead to an overworked immune system and chronic inflammation in the body.


Cow’s milk allergy is the most common allergy in children under 5 years old. It remains a top allergen into adulthood, affecting up to 1 in 13 adults.

Asthma, Sinus issues, and Other Respiratory Problems

The casein in dairy can cause increased mucus production in the airways and lungs. Over time, this excess mucus may lead to asthma symptoms and recurrent sinus problems like chronic sinusitis.

Researchers from Harvard and other universities explored the diets of nearly 700 children of color to better understand the link between food, inflammation, and our airways. Of all the foods they looked at (including sweets), dairy products were the most problematic, nearly doubling the odds of childhood asthma.

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Sharon McDowell Ironman Race Hawaii 2022

Eczema, Acne, and Other Skin Conditions

There are multiple studies that support a link between acne and dairy consumption. A dairy allergy can also cause a delayed reaction, manifesting as eczema.

When scientists from Harvard and other universities studied almost 80,000 children, teens, and young adults, they found that drinking just 1 glass of milk per day increased their chances of having acne by 41%.

Although more research is needed, those with chronic skin issues tend to report clearer skin after eliminating dairy from their diets.