More serious than lactose intolerance
Unfortunately, milk allergy is often confused with a milk-related digestive problem. Globally, about 70% of people lack the enzyme to break down the sugar in milk; the condition, known as lactose intolerance, can cause bloating, abdominal cramps, and diarrhea but is not life-threatening.
“Because lactose intolerance is so common, people don’t think of milk allergy as something that can be significant or severe,” said Ruchi Gupta, MD, MPH, director of the Center for Food Allergy and Asthma Research at the Northwestern University, Chicago.
In babies, colic, the regurgitation of milk-based formula, and rash are sometimes misinterpreted as a milk allergy, leading parents to buy expensive, specialized formula unnecessarily.
Frustrated by a lack of data about food allergies, Dr. Gupta and colleagues launched a nationally representative survey of 38,408 American parents in 2009, which was updated in 2015 and 2016.
On average, children with milk allergy had their first reaction before the age of 2, most commonly vomiting, diarrhea, hives, and eczema; this is a younger age of onset than for other food allergies. And children with milk allergy were twice as likely as children with other allergies to grow out of it.
Yet about one-third of milk-allergic children in the updated study were 11 years and older. And in a similar survey of adults who self-reported symptoms, milk allergy was as common as peanut allergy (1.9% vs 1.8%). “We don’t know why milk allergy is becoming more persistent,” Dr. Gupta said. And, she warned, only one in four children with a milk allergy had a current prescription for an epinephrine autoinjector, compared with about 70% of children with peanut allergy.
Food allergy can’t be caused by genetics alone, said Christine Olsen, MD, cofounder and CEO of the Food Allergy Science Initiative at the Broad Institute in Cambridge, Mass. “There may be a genetic predisposition, but there must be something environmental” that has influenced the development of food allergies.
One theory is that the body’s natural defense against noxious substances has been disrupted in the modern world by processed foods, chemical additives, and hygienic surroundings.
Dr. Olson’s own son vomited when he had his first small taste of hummus as a baby; he is severely allergic to sesame. The immediacy of his bodily reaction made Dr. Olsen think that the response involved neurons, not just a misguided immune system.
Researchers are currently looking for drug targets that could shut off the immune response as quickly as it starts. If you think of the fact that some kids outgrow their allergies and some adults get allergies, that suggests there’s some lever that you can turn on and off,” said Dr. Olsen, who is also a radiation oncologist.
Preventing allergy
The approach to food allergy prevention has already been transformed by the Learning Early About Peanut Allergy (LEAP) study conducted in the United Kingdom. LEAP investigators randomly assigned 640 infants to ingest regular amounts of peanut snacks or peanut butter or to avoid peanut products until they reached 5 years of age. The babies who had regular exposure to peanut from an early age were much less likely to develop a peanut allergy than those who avoided peanuts.
The National Institute of Allergy and Infectious Diseases revised its guidelines and now recommends that all babies be exposed to peanut-containing food at around 6 months of age; for high-risk babies, that can start as early as 4 months.
Allergy experts are planning to study that concept again with other foods, including cow’s milk. The 5-year iREACH study, launched by the Center for Food Allergy & Asthma Research at Northwestern and Lurie Children’s Hospital in Chicago, is currently enrolling 10,500 infants to test early exposure to peanuts, milk, egg, and cashew. A portion of the infants will have severe eczema, putting them at high risk for food allergies, and others will be low risk, said Dr. Gupta, who is the principal iREACH investigator.
“Hopefully in the next 5 years we will have data showing whether this prevention technique will work for other common food allergens, in addition to peanuts,” she said.
Introducing foods early “promotes tolerance rather than early sensitization,” explained Stephanie Leeds, MD, an allergist and immunologist at Yale University, New Haven, Conn. In the future, rather than just diagnosing and treating food allergies, allergists might work with pediatricians to help prevent them from ever happening.
A version of this article first appeared on Medscape.com.