20 Million Americans Live With Food Allergies as Doctors Warn Cases Are Rising

The American Medical Association’s What Doctors Wish Patients Knew series offers a rare window into the clinical realities behind today’s health headlines. In this installment, two specialists in allergy and immunology share what they most want patients and families to understand about food allergies what they are, what they are not, and why precision matters.

Amber Burnette, MD, an allergist and immunologist with the Southern California Permanente Medical Group in Garden Grove, California, and assistant area medical director for Kaiser Permanente Orange County, joins Zachary Rubin, MD, a pediatric allergist and immunologist based in Oak Brook, Illinois. Together, they outline the science behind allergic reactions and clarify misconceptions that often cloud patient understanding.

At its core, a food allergy is an abnormal immune response. Unlike a mild sensitivity, an allergy involves the immune system misidentifying a harmless food protein such as peanut or shellfish as a threat. The result can range from hives and swelling to breathing difficulty, vomiting, a dangerous drop in blood pressure, or even life-threatening anaphylaxis. These reactions typically occur within minutes to two hours after ingestion, often while a person is still eating the meal in question.

Food Allergy vs. Food Intolerance: A Critical Distinction

One of the most common questions patients ask is about the difference between allergy and intolerance. Though the terms are frequently used interchangeably in casual conversation, medically they describe entirely different mechanisms. An allergy originates in the immune system; an intolerance stems from the digestive tract.

Food intolerances occur when the body struggles to break down or process a component of food. Symptoms such as bloating, abdominal pain, gas or diarrhea can be uncomfortable and disruptive, but they are not life-threatening. The immune system is not mounting an attack; rather, digestion is incomplete or inefficient.

A classic example is lactose intolerance, in which the body lacks sufficient amounts of the enzyme needed to digest lactose, the sugar found in milk. The result is gastrointestinal distress, not anaphylaxis. Understanding this distinction empowers patients to respond appropriately and avoid unnecessary fear while still seeking proper evaluation.

Not All Food Allergies Behave the Same Way

Food allergies are not a single uniform condition. Instead, they fall into three broad categories, each with distinct patterns of symptoms and treatment strategies. The first and most widely recognized type is IgE-mediated food allergy. These reactions occur rapidly within minutes to two hours and may include hives, swelling, vomiting, wheezing or trouble breathing. Because they can escalate quickly, epinephrine remains the primary treatment.

A second category involves non-IgE-mediated food allergies, which tend to produce delayed gastrointestinal symptoms. These reactions may emerge several hours after eating and can include severe vomiting, diarrhea, or blood and mucus in the stool particularly in infants. One example is food protein-induced enterocolitis syndrome, or FPIES, which can lead to repeated vomiting and dehydration. Unlike IgE-mediated reactions, epinephrine does not treat these delayed responses.

Finally, some conditions involve a blend of immune pathways. Eosinophilic esophagitis, often abbreviated as EoE, is one such disorder. In EoE, certain foods trigger chronic inflammation of the esophagus, leading to difficulty swallowing, feeding problems or persistent vomiting. Rather than a sudden reaction, symptoms tend to be ongoing and require long-term management.

Why Food Allergies Develop and What Patients Should Understand

There is no single cause of food allergies. Physicians describe them as multifactorial, shaped by a convergence of genetics, environment and early-life exposures. A family history of food allergy increases risk, but inheritance alone does not determine outcome.

Skin health plays a significant role. Children with eczema, for example, face a higher likelihood of developing food allergies. When the skin barrier is disrupted and inflamed, exposure to food proteins through the skin may promote sensitization a process in which the immune system begins producing IgE antibodies that later trigger allergic reactions.

Emerging research also points to the gut microbiome. Early antibiotic use, acid-suppressing medications, cesarean delivery and even vitamin D deficiency have been associated with increased allergy risk, possibly due to their influence on how the immune system learns to tolerate food proteins. While no single factor tells the whole story, the broader message is clear: food allergies arise from a complex interplay of biology and environment, and understanding that complexity is the first step toward informed, compassionate care.