Scientists Discover Why Food Allergies Trigger Severe Reactions—and It's Not What They Thought

For decades, scientists believed all severe allergic reactions followed the same pathway in the body, with histamine as the main culprit. But groundbreaking research from Arizona State University and Yale University has uncovered a surprising twist: when you eat something you're allergic to, your gut responds completely differently than when allergens enter your bloodstream directly.

What Makes Food Allergies Different from Other Allergic Reactions?

The key difference lies in specialized immune cells called mast cells that line your intestines. When these gut-based mast cells detect a food allergen, they don't release much histamine—the chemical that antihistamines are designed to block. Instead, they pump out inflammatory molecules called cysteinyl leukotrienes, the same chemicals that cause airway constriction during asthma attacks.

"Until now, we assumed that anaphylaxis followed the same pathway regardless of where allergens entered the body, with histamine from mast cells as the main driver," says Dr. Esther Borges Florsheim, researcher at ASU's Biodesign Center for Health Through Microbiomes. "Our study shows that when allergens are ingested, a specialized set of mast cells in the gut don't release histamine—instead, they produce lipid-based molecules called leukotrienes."

How Did Researchers Test This Discovery?

The research team used zileuton, an FDA-approved asthma medication that blocks leukotriene production, to test their theory. The results were striking: the drug reduced allergy symptoms and protected against the dangerous drop in body temperature that signals anaphylaxis—but only when allergens were eaten, not when they were injected into the bloodstream.

This finding explains a long-standing medical puzzle: why measuring food-specific antibodies, especially immunoglobulin E (IgE), doesn't reliably predict who will have severe food allergic reactions. The gut's unique response system operates differently than what doctors previously understood.

What Does This Mean for Food Allergy Treatment?

The discovery opens up new possibilities for preventing and treating food-triggered anaphylaxis. Current emergency treatments like epinephrine are designed to reverse symptoms after anaphylaxis begins, while antihistamines often prove ineffective for severe food reactions.

Several existing asthma medications that target leukotrienes could potentially be repurposed for food allergy prevention:

• Zileuton: Blocks the enzyme needed to produce leukotrienes and showed protective effects in the study
• Montelukast: Blocks leukotriene receptors and is commonly prescribed for asthma management
• Leukotriene inhibitors: Already FDA-approved for other conditions, which could speed up testing for food allergy applications

Meanwhile, climate change is making seasonal allergies worse for millions of Americans. The freeze-free growing season has lengthened in 87% of 198 U.S. cities analyzed since 1970, with these cities seeing their pollen season extend by 20 days on average. Cities in the Northwest saw the largest increase at 24 additional days, while Southwest cities gained 20 extra days of potential pollen exposure.

The research team plans to study whether similar mast cell populations and leukotriene-driven pathways exist in human intestines, and whether blocking them can reduce severe reactions in people with life-threatening food allergies. This gut-focused approach represents a fundamental shift in how scientists understand and potentially treat food allergic reactions.

Separately, researchers are also developing experimental vaccines that show promise in preventing deadly allergic reactions in mice for up to a year, suggesting multiple new approaches may soon be available for managing severe allergies.