Stephanie Leeds' interest in allergy begins with a classic story of mentorship, and the incredible allergists and immunologists who offered her guidance and advice early in her medical career.
"With early exposure to the field, I just felt very much at home and was shepherded into the community in a really organic way," said Leeds, now associate professor of pediatric allergy and immunology at Yale School of Medicine. "My mentors showed me what was possible in the field of allergy and immunology."
Today, Leeds is a pediatric allergy and immunology physician who specializes in food allergy. Almost a third of adults and children in the U.S. have at least one allergy, according to the Centers for Disease Control and Prevention's National Center for Health Statistics. That includes food allergies like shellfish, peanuts, and milk.
Typically, the only treatment for food allergies has been avoidance, Leeds says. But that's starting to change, as the field shifts its focus to prevention and early treatment.
"To offer hope and early treatment to families, even with children who have incredibly severe allergic disease, is just really wonderful," she said.
In an interview, Leeds explains why it's difficult to pin down why some kids develop allergies and others don't, what factors cause an allergy diagnosis to evolve, and what treatments are available for children today.
The interview has been edited for length and clarity.
What causes some infants and toddlers to develop allergic conditions?
Stephanie Leeds: We don't know the exact reasons why. As with most things, it's multifactorial, but there's probably a genetic predisposition component. There's probably an environmental and exposure component. While we can identify some risk factors, we don't know the exact mechanisms of why allergies develop in children.
How permanent is an allergy diagnosis?
Leeds: That's an interesting question. There's something called the atopic march, which people often think about as the development and evolution of allergic diseases in an individual over time. For example, a baby starts out having eczema, and then might develop some food allergies, maybe asthma. This happens in a stepwise approach. For some kids, they have allergic diseases that abate or improve with time and age. Others have allergic diseases that persist or worsen over time. So again, we don't understand the full mechanism, or the profile factors that might increase the chances of someone outgrowing their allergic diagnoses. But we've tipped the scales a little bit recently and started with some interventional therapies for allergic conditions in young infants and toddlers to try and modulate the immune system toward tolerance over allergy.
What causes an allergy diagnosis to evolve?
Leeds: Let's talk about food allergy because I'm primarily a food allergist. The natural history of food allergy really depends on a lot of different factors, one of them being the food itself that someone is sensitized to. For the vast majority of kids who have such allergies as egg or milk allergy, they will outgrow it. As they get older, they will develop waning antibody sensitization to the proteins in eggs and milk. Most children outgrow these allergies in a stepwise fashion where, for example, they'll start to tolerate baked milk or baked egg, and then in subsequent years and months afterwards, they'll start tolerating other forms of milk and eggs. That's epidemiologically the natural history of those foods. It probably has something to do with the protein structure of the food itself. It probably also has something to do with the way we process, bake, and eat those foods. But there are other foods, for example, like peanuts, tree nuts, and seeds in which the vast majority of kids will not outgrow their food allergy. Again, it may have something to do with the inherent protein structure of the foods themselves.
Can allergy, including food allergy, be prevented in infants and toddlers?
Leeds: We're trying our best. There was a groundbreaking study called the LEAP [Learning Early about Peanut Allergy] study. It was revolutionary in that it showed that early and consistent introduction of peanut could prevent food allergy in many high-risk infants. We certainly have learned lessons about, for example, early food introduction for the prevention of food allergy.
We've also learned some lessons about how to treat food allergy if it develops early enough to potentially push the immune system toward tolerance over allergic sensitization. Not all children will have prevention of food allergy with early introduction; some will still react. Luckily, we have interventional treatments for those patients, too. A lot of it is focused on early identification, accurate diagnosis, and shared medical decision-making around all the options that are available to families with young infants and toddlers with food allergy.
What does treatment for allergic conditions in young children look like today?
Leeds: It depends on the allergic condition we're talking about. For food allergy, we often talk a lot about options including avoidance, which was standard of care for a long time. But today there is also oral immunotherapy, where we give small amounts of food allergens daily to try and increase tolerance levels over time. We also have a whole class of medications called biologics, which are targeted biologic molecules that affect the allergic arm of the immune system, primarily interacting cytokine signaling and allergic antibodies that contribute to the development of allergic disease. So there are now injectable medications that are targeted that can treat anything from eczema to asthma to food allergy.
