You Can’t Predict Allergic Reactions, But Asthma and Exercise Are Risk Factors, Top Allergy Expert Says

Asthma ImageEditor’s note: Please note that this conference report is from FARE’s 2013  conference.

While it is virtually impossible to predict future food-induced allergic reactions, co-existing asthma is a key factor in whether someone will be prone to more severe allergic reactions, Dr. Robert A. Wood, chief pediatric allergist at Johns Hopkins Children’s Center, said May 18, 2013.

“If somebody has asthma, especially if your asthma is more poorly controlled, you’re going to be at a higher risk of having a more severe reaction,” Dr. Wood said at Food Allergy Research & Education’s 20th annual allergy conference in Arlington, Va.

Driving the point home, the internationally recognized food allergy expert said, “It’s very hard to find deaths from food allergies in kids who don’t have asthma.”

For parents like me who have a child with food allergies, being prepared for potential allergic reactions–especially severe ones–is always at the forefront of our minds.

Throughout his presentation, Dr. Wood spoke to us about the risk factors for more severe allergic reactions and addressed other areas of managing food allergies in our children.

(This article is my third in a series of special reports on FARE’s 2013 annual conference. Check out my related coverage: how to recognize and treat anaphylaxis and specific nutritional factors that may be at play.)

Key Factors for More Severe Allergic Reactions.

Dr. Wood said the severity of an allergic reaction may depend on a few key factors:

  • an individual’s sensitivity to the allergen,
  • the dose of the allergen,
  • the route of exposure, and
  • other factors like asthma, exercise, or infection.

“We do worry more about people with co-existing asthma,” Dr. Wood said.

Moreover, the dose of the allergen is probably going to be the biggest variable that you can’t predict, he advised.

Dr. Wood used as an example the child whose initial allergic reaction to peanut is a cross-contaminated baked good with one-one hundredth of a peanut, and their reaction after that is to a baked good that contains four peanuts, or four hundred times the first dose. The child’s second reaction “is going to be a lot worse than the first one,” he stressed.

“That’s why you can never say ‘I know my child reacted this way, so next time they’re going to react that way,’ because you don’t know what dose they’re going to be exposed to,” he warned.

Top Four Risk Factors for Fatal Anaphylaxis.

Most importantly, Dr. Wood said that in addition to co-existing asthma, there are three other risk factors for fatal food-induced anaphylaxis:

  • having a peanut and tree nut allergy,
  • having had a prior episode of anaphylaxis, and
  • failing to treat promptly with epinephrine.

Should Exercise Be Restricted After Dosing?

During the question-and-answer session, Dr. Wood was asked about three particular approaches to treating food allergy with immunotherapy: oral (OIT), sublingual (SLIT), and baked OIT treatments.

In particular, he was asked what his clinic does in terms of restricting exercise for periods before or after these treatments.

In response, he said that when they are treating patients–only the most highly allergic people who are going to have reactions at some point–with SLIT or OIT, they strongly recommend restricting exercise two hours after dosing if at all possible.

“So we recommend dosing in the evening, when things are quiet and you don’t need to run around for a few hours,” he said.

You Can’t Predict Next Reaction.

Dr. Wood told the group to remember that anaphylactic reactions can vary widely, even in the individual child.

“The variability in what your body reacts to makes it virtually impossible to predict your next reaction,” Dr. Wood said.

“Another myth is that you can predict a future reaction based on your prior reaction history,” he said. “The reality here is, again, that there is no predictable pattern.”

For example, he said, “The child who has milk, egg, soy, peanut, and wheat allergies might react with anaphylaxis to milk and egg and less so to wheat, or they might react most severely to wheat and less so to peanut.”

On the heels of the death of a child in New Jersey who had a milk allergy, Dr. Wood reminded the audience that peanut and tree nut allergies are the most common cause of fatal reactions, but that they aren’t the only foods that produce severe reactions.

“There’s not any food that gives a more predictably severe reaction,” Dr. Wood said.

“But even moreso, with the very same food, you might react very differently from one reaction to another,” he added.

Studies Show Unpredictability of Reactions.

To emphasize the unpredictability of allergic reactions, Dr. Wood talked about some of his studies.

To start, he explained that in their studies, they have given their patients carefully measured doses of the exact same food protein with the exact same dose on a daily basis.

What they have found is that over a course of 50 days, for example, they may see them have 30 days with no symptoms, 15 days with an itchy mouth, 3 days where they got a little bit more congested, and 2 of them where they have anaphylaxis; all with the same dose, he said.

“Everything else is the same,” he stressed. “Two days out of 50 they needed epinephrine. The other 48 they were fine. And that’s one of the things that we learned the most from our treatment studies: You cannot predict your next reaction.”

Always Be Prepared to Treat With Epinephrine.

Dr. Wood went on to discuss what is always on the mind of someone like me, a parent whose child has food allergies: Can anaphylaxis be prevented?

“We prevent it by saying that complete avoidance is impossible and that reactions can never be predicted,” he said. “We never want to think, ‘Okay, my child is only doing this today, so they’re really not at risk for a reaction.’ ” 

Thus, Dr. Wood advised everyone to be prepared to treat a reaction at all times, have a clear action plan, always have self-injectable epinephrine on hand, and have everyone trained in administering the epinephrine.

“If you have it there and no one’s ready to use it, you’re still in trouble,” Dr. Wood told the group.

Food Allergy Research & Education (FARE) is a nonprofit organization that provides advocacy and education on behalf of individuals with food allergies. For more information about FARE, please visit their website at

Do you have asthma and food allergies? Have you experienced an allergic reaction while exercising? We’re interested in hearing about your experiences.