Allergology (ALLERGIES) with Zachary Rubin

What It Covers

Double board-certified allergist and immunologist Dr. Zachary Rubin, author of the New York Times bestselling book *All About Allergies*, explains the biological mechanisms behind allergic reactions, food allergy development in children, the difference between allergies and intolerances, at-home testing accuracy, oral allergy syndrome, antihistamine side effects, and immunotherapy as the only disease-modifying treatment currently available.

Key Questions Answered

• •Early peanut introduction: A landmark clinical trial found that introducing peanuts before age one resulted in an 80% lower rate of peanut allergy development compared to delayed introduction. Current guidelines, updated around 2015, recommend early exposure to highly allergenic foods under pediatric guidance. This shift has contributed to a measurable decline in peanut allergy rates, with egg now surpassing peanut as the most common food allergen in infants.
• •At-home food sensitivity testing: IgG-based mail-in food sensitivity tests measure a tolerance antibody, not an allergy antibody, meaning any food regularly consumed will appear as a positive result. These tests carry a high false-positive rate, cost $100–$300, and frequently lead to unnecessary food elimination. Eliminating foods a child tolerates can actually induce a genuine, potentially lifelong IgE-mediated food allergy upon reintroduction.
• •Oral allergy syndrome cross-reactivity: People with pollen allergies frequently experience itching, mild swelling, or throat irritation when eating certain raw fruits, vegetables, and nuts due to structural protein similarities between pollen and food. Birch tree allergy cross-reacts with apples, cherries, kiwi, carrots, celery, almonds, and peanuts. Cooking, canning, freezing, or microwaving the food typically breaks down the protein enough to eliminate the reaction entirely.
• •Antihistamine withdrawal risk: The FDA now requires warning labels on second-generation antihistamines including Zyrtec and Zyzal, acknowledging that stopping these medications abruptly after three or more months of daily use can trigger severe, widespread itching requiring medical intervention. Patients should taper dosage slowly rather than stopping suddenly, and should discuss any long-term antihistamine use with a physician before discontinuing.
• •Allergy shots as disease modification: Subcutaneous immunotherapy injections are the only treatment that addresses the underlying immune dysfunction rather than masking symptoms. By gradually increasing allergen exposure near lymph nodes over time, the immune system learns tolerance. An emerging variation called intralymphatic immunotherapy delivers injections directly into groin lymph nodes under ultrasound guidance, achieving similar results significantly faster due to proximity to the immune response source.
• •Pollen season worsening due to climate: Rising temperatures and elevated atmospheric CO2 levels are measurably extending pollen seasons, with earlier start dates, later end dates, and higher pollen grain counts per season. Controlled studies growing trees under varying CO2 concentrations confirmed a direct relationship between CO2 levels and pollen output. This environmental shift, not the widely circulated botanical sexism theory about male street trees, explains the documented increase in seasonal allergy severity.