By Kaitlin Sullivan - NBC News
Eczema in babies could be a sign that the child will develop more allergies.
New research, published Tuesday in the journal Pediatrics, confirms a phenomenon known as "allergic gait," a pattern that describes how allergies tend to develop and progress in children from infancy to age 3.
The study, which analyzed data from medical records collected between 1999 and 2020 from more than 200,000 children, found that children were often first diagnosed with eczema, also called atopic dermatitis, at 4 months, on average.
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Food allergies, which cause symptoms ranging from hives to anaphylaxis — a life-threatening allergic reaction that affects the entire body and can cause the airways to swell and close — and asthma, both around 13 months, were then diagnosed.
At 26 months, according to the study, the children developed allergic rhinitis, or hay fever. Rarely, children may develop a fifth allergy, called eosinophilic esophagitis, by 35 months.
Dr. Stanislaw Gabryszewski, a member of the Division of Allergy and Immunology at Children's Hospital of Philadelphia who led the study, noted that "allergic walking" does not mean that all children with eczema develop all of the allergies described.
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"Every child is different. Some may have one, some may have a pair, some may have them all," he said.
About one in five children suffers from one of these types of allergies, making them one of the most common chronic diseases in children. According to the researchers, just over 13% of children suffer from at least two types of allergic conditions.
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The results are useful for both parents and doctors, who can more closely monitor children who develop eczema at an early age for other allergies later.
"Early eczema is the first risk factor for developing allergies later in life, much more so than family history," says Dr. Ruchi Gupta, founding director of the Food Allergy and Asthma Research Center at Northwestern University and Lurie Children's Hospital of Chicago, who was not involved in the study.
The medical community has long recognized allergic march, but the new research is the largest study to confirm the pattern. And while previous research focused primarily on white children, about one-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 further evidence that allergic diseases start early in life, and that there is a progression of allergic diseases 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.
He added that sometimes the first allergic conditions disappear and the child only has one food allergy, for example, but other times the allergies are cumulative and children suffer from several types of allergies. For some, certain allergies come and go, according to Chinthrajah.
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Food allergies were less common than had been seen in previous research, affecting about 4% of the children in the study, about half of what was seen in studies in which people self-reported their allergies. The most frequent food allergies were to peanuts, eggs and shellfish. Patients with respiratory allergies, such as asthma and allergic rhinitis, often suffered from both conditions, in addition to other allergic disorders.
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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 with the disease were not white. In general, this allergy was very rare, as it was only seen in 0.1% of children.
A better understanding of how allergies typically develop could lead to treatments that halt their progression or prevent their onset altogether.
If eczema can be prevented, "can we prevent food allergies, environmental allergies, and can we prevent asthma?" Gupta asked. "We don't know yet, but it's being investigated."
Chinthrajah agreed.
"Our job as researchers is to determine how to intervene early and, with those interventions, how to influence not one of the five allergic diseases, but many," he explained.
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That research will have to unravel the relationship between environmental factors — including climate change, which is worsening seasonal allergies — and genetics.
"Ultimately, the interaction of both factors will determine which children develop allergies and, if so, their severity," explains Gabryszewski.