The ‘allergic march’ shows how allergies can progress in children

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Eczema in young babies could be a sign that a child will develop more allergies.

New research, published Tuesday in the journal Pediatrics, confirms a phenomenon known as the «allergic march,» a pattern that describes the way allergies tend to develop and progress in children, from infancy to age 3.

The study, which analyzed medical record data collected between 1999 and 2020 from more than 200,000 children, found that children tended to be first diagnosed with eczema, also called atopic dermatitis, at 4 months, on average. Then came diagnoses of food allergies causing symptoms. ranging from hives to anaphylaxis, a life-threatening allergic reaction that affects the whole body and can cause the airways to swell and close, and asthma, both around 13 months of age. By 26 months, the study found, the children developed allergic rhinitis, or hay fever. In rare cases, children can develop a fifth allergy, called eosinophilic esophagitis, at 35 months of age.

Dr. Stanislaw Gabryszewski, a member of the Division of Allergy and Immunology at Children’s Hospital of Philadelphia who led the study, said the «allergy march» does not mean that all children who have eczema will develop all the allergies described.

“Every child is different. Some may have one, some may have a couple, some may have all of them,” she said.

About 1 in 5 children have one of these types of allergies, making them one of the most common chronic diseases in children. Slightly more than 13 percent of children have at least two types of allergic conditions, the researchers said.

The findings are useful to both parents and doctors, who can more closely monitor children who develop eczema early in life for other allergies later.

«Eczema early in life is the number one risk factor for developing allergies later in life, far more so than family history,» said Dr. Ruchi Gupta, founding director of the Northwestern University Food Allergy and Asthma Research Center and Children’s Lurie Hospital of Chicago, who was not involved in the study.

The medical community has long recognized the allergic march, but the new research is the largest study to confirm the pattern. And while previous research focused primarily on white children, around a third of the children in this study were black. About 10% were Hispanic and a smaller proportion, less than 3%, were Asian or Pacific Islander.

«This study adds another layer of evidence that allergic diseases start early in life, and there is a progression of allergic disease that can occur together, so that a child can have multiple allergic conditions,» said Dr. Sharon Chinthrajah, an immunologist at Stanford University School of Medicine who was not involved in the research.

She added that sometimes previous allergic conditions go away and the child is left with just one food allergy, for example, but other times the allergies are cumulative, leaving children with multiple types of allergies. For some, certain allergies come and go, Chinthrajah said.

Food allergies were less common than previous research found, affecting about 4% of children in the study, about half the number seen in studies where people self-report their allergies. The most common food allergies were peanuts, eggs, and shellfish. Patients with respiratory allergies such as asthma and allergic rhinitis usually had both conditions, in addition to other allergic conditions.

The study also found that eosinophilic esophagitis, a rare type of food allergy that causes inflammation in the esophagus, affects a higher proportion of non-white children than previously thought. About 40% of children who had the condition were not white. Overall, this allergy was very rare, occurring in only 0.1% of children.

A better understanding of how allergies commonly develop could lead to treatments that could stop the progression, or stop the development of allergies altogether.

If eczema could be prevented, «can we prevent food allergies, environmental allergies, and can we prevent asthma?» Gupta asked. «We don’t know yet, but it is being investigated.»

Chinthrajah agreed.

“Our job as researchers is to identify how we intervene early and with those interventions, how we influence not one of the five allergic diseases but many,” he said.

That research will need to untangle the link between environmental factors, including climate change, which is making seasonal allergies worse, and genetics.

«Ultimately, it’s the interaction of the two that will dictate which children develop allergies, and if they do, how severe they will be,» Gabryszewski said.

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