277 ‒ Food allergies: causes, prevention, and treatment with immunotherapy | Kari Nadeau, M.D., Ph.D

KEYPOINTS

• 01

  Food allergy is driven by IgE, a tiny but potent antibody class.

  Nadeau, an allergist-immunologist and immunotherapy pioneer, explains that IgE represents about 0.005% of the immunoglobulins in blood—the least concentrated class—yet triggers mast cells and basophils to release histamine and other mediators, causing hives, swelling, vomiting and potentially fatal anaphylaxis. For every IgE molecule, the body can make about 100 IgG molecules, which become important in tolerance.

• 02

  Food allergies are common and becoming more persistent.

  Her colleague Ruchi Gupta's data show about 1 in 12 U.S. children have a food allergy, and roughly 1 in 30 adults—whether persisting from childhood or newly developed. Nadeau trained when children under five with milk or egg allergies had an 80% chance of outgrowing them; now it's closer to 50%. Peanut, tree nut, shellfish and fish allergies usually persist (about 80%).

• 03

  It's largely environmental, not genetic.

  Nadeau says roughly 70–80% of food allergy risk isn't genetic. A key insight is the 'dual allergen exposure' idea: allergens encountered through inflamed skin (eczema) tend to sensitize, while those eaten early tend to build tolerance.

• 04

  Old avoidance guidelines likely made things worse.

  Twenty years ago, well-meaning guidelines—based on as few as about 20 individuals—told pregnant women and families to avoid peanuts and tree nuts and delay introduction. Later, much larger studies showed it's fine to eat peanuts and tree nuts during pregnancy and that early introduction lowers risk.

• 05

  Introduce allergenic foods early, alongside breastfeeding.

  WHO recommends breastfeeding, and Nadeau says families should also start other foods, including common allergens, around 4–6 months. She doesn't think we'll fully return to prevalence levels of 30 years ago, but prevention can bend the curve.

• 06

  Reactions are unpredictable, and cofactors matter.

  The same dose can produce worse reactions with repeated exposure, and factors such as exercise, illness or altitude can change severity—one reason allergic people must always carry epinephrine.

• 07

  Oral immunotherapy retrains the immune system by giving tiny, increasing doses of the allergen.

  The principle dates back about 100 years with environmental allergies. For peanut, therapy starts around 1/200th of a peanut, increasing about 25% every two weeks; once patients reach about 40–60 mg, steps can be skipped. Shots aren't used for foods because foods are too potent in a specific IgE disease.

• 08

  Treatment has gotten faster as the immune switch became visible.

  Researchers learned by about 3 months the immune response begins shifting, allowing faster dose increases by 6 months, and by a year the immune system has switched—it shouldn't take 10 years. Many patients target 600 mg (protecting against accidental ingestion), a threshold the FDA also uses.

• 09

  Time on maintenance determines the chance of cure.

  After at least 2 years on dose, about 20% reach the 'cure' category (eating freely after stopping); after 5 years, about 60%. For some allergens, after 5 years of immunotherapy, roughly 25% regain the allergy, 25% have it reduced, and 50% have it resolved for life.

• 10

  Modern protocols are very safe.

  Because dosing goes 'low and slow', epinephrine is needed during dosing only about 1 in 10,000 times, or 1 in 100,000 in some trials. Combination with biologics like anti-IgE can help.

• 11

  PM2.5 air pollution is a major and underappreciated hazard.

  PM2.5 particles are 2.5 microns—smaller than a red blood cell—so they penetrate lungs and enter blood. The category contains about 200 chemicals, including volatile organic compounds. Wildfire smoke, even more potent, can circle the globe within four days. Pollution kills an estimated 8–10 million people a year, and she calls it more dangerous than tobacco smoke because it's so prolific.

• 12

  Protect yourself indoors and outdoors.

  Check AirNow; in the yellow zone, wear a mask, and outdoor workers should wear an N95 when AQI is around 100. She advises patients not to exercise outdoors when AQI exceeds about 50. We spend over 90% of time indoors, so use MERV 13 or higher filters (not MERV 7–8) and watch gas or wood stoves.