A teenage girl in Canada had an unusual food allergy that showed up only after she exercised, according to a new report of her case. 

The 17-year-old's allergy first appeared when she had a small snack — a few rice crackers and hummus — right before she worked out on a treadmill at her home. She ran for just 10 minutes before her lips started to swell. She stopped running, but her symptoms became severe, and she developed the puffy eyes, hives, itching and abdominal pain that occur in the body-wide allergic reaction known as anaphylaxis.

The girl was taken to the emergency room and treated with Benadryl and epinephrine, and she recovered about 3 hours later, the report said.

"We hope that this case will serve as an important reminder that although rare, food-dependent exercise-induced anaphylaxis exists and making a diagnosis can lead to life-saving preventative strategies," the researchers at Montreal Children's Hospital, who worked on the girl's case, wrote in their report, published online Sept. 3 in the Journal of Medical Case Reports.

The girl later went to an allergy clinic, where testing revealed that chickpeas had triggered her allergic reaction.

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However, the girl had previously eaten chickpeas on a number of occasions without any symptoms, and she had never experienced allergic symptoms after exercising, when she hadn't eaten chickpeas. [8 Strange Signs You're Having an Allergic Reaction]

The doctors suspected that the girl had food-dependent exercise-induced anaphylaxis, or FDEIA, a rare allergy that occurs only when a person consumes a particular food just before exercise. People with the condition don't react to either the food or the exercise by itself.

Unlike other food allergies, FDEIA is more common in teens and adults than in children, the researchers said.Exactly why the allergy occurs only after exercise is not clear. It's thought that the physical effort needed in exercise triggers a physiological change that enhances the absorption of the allergen in the intestines, the researchers said.

The doctors recommended that the girl avoid eating chickpeas, or foods like hummus that contain chickpeas, 2 hours before or after exercise. Since her diagnosis, the girl has eaten hummus and fresh chickpeas without exercising, and she has not experienced any allergic reactions, the researchers said.

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