For decades, pediatricians recommended delaying the introduction of major allergens to reduce allergy risk in at-risk children. This recommendation proved not only ineffective but potentially counterproductive. The breakthrough came in 2015 with the LEAP study (Learning Early About Peanut Allergy), published in the New England Journal of Medicine, which transformed pediatric allergology worldwide.

The LEAP Study: The Early Introduction Revolution

The LEAP study followed 640 infants at high risk for peanut allergy (with severe eczema or egg allergy). They were randomly assigned to two groups: peanut introduction at 4-11 months of age versus avoidance until age 5. At age 5, results showed that 17% of the avoidance group had developed peanut allergy, compared to just 3% of the early introduction group. The risk reduction with early introduction was 80%. This study overturned guidelines worldwide.

New Guidelines: Early Introduction of Allergens

ESPGHAN (2022), the American NIAID, and the Italian SIP now agree on this principle: allergens should not be delayed compared to introducing other foods. This applies to all major allergens: peanuts, eggs, fish, wheat, soy, dairy, and tree nuts. The optimal introduction window appears to be between 4 and 6 months during weaning. Introducing allergens after 12 months in high-risk children seems to increase allergy risk.

How to Introduce Allergens Safely

Introduce one allergen at a time, waiting 2-4 days before the next to identify any culprit. Offer the first taste of a new allergen at home (not at a restaurant) at a time when you can observe your baby for 2 hours. Start with small amounts (half a teaspoon). First offerings: cooked egg yolk, cooked white fish (boiled cod), natural peanut butter diluted in puree (not whole peanuts: choking risk), finely blended cooked lentils.

High-Risk Infants: When to See an Allergist

Children with severe uncontrolled eczema or first-degree family history of severe food allergy: for these children, NIAID recommends consulting an allergist before introducing peanuts and other high-risk allergens to evaluate skin prick testing and possible controlled introduction in the office. Don't delay introduction waiting for an appointment, but address it with appropriate professional support for high-risk cases.

Recognizing an Allergic Reaction in Infants

Signs of acute allergic reaction appear within 15-30 minutes of ingestion. Mild symptoms: hives (red bumps on skin), redness around the mouth, swollen lips, runny nose, watery eyes. Severe symptoms (anaphylaxis): difficulty breathing, stridor, sudden paleness, hypotonia (floppy baby), loss of consciousness. Mild symptoms: stay calm, observe, call your pediatrician. Severe symptoms: call emergency services immediately without waiting for further developments.

Severe Eczema and Allergy Prevention

Skin damaged by eczema allows food proteins to enter through the skin and sensitize the immune system, rather than being introduced orally (which tends to produce tolerance). For this reason, aggressively treating eczema with emollients recommended by a dermatologist is part of food allergy prevention: not just for your baby's comfort, but to reduce the risk of sensitization to foods before they've ever eaten them.

Allergen Introduction Timeline: Practical Guide

A possible schedule for children without high-risk factors: week 1 of weaning: hard-boiled egg yolk. Week 2: wheat (pasta or very well-cooked soft bread). Week 3: cooked white fish (boiled cod or plaice). Week 4: natural peanut butter diluted (1/4 teaspoon in puree). Week 5: lentils and other cooked legumes. Week 6: finely chopped cooked shellfish. Your pediatrician is your reference for personalizing this schedule based on your baby's family history.

Allergy vs. Intolerance in Infants: How to Tell the Difference

CMPA (cow's milk protein allergy) is the most common food allergy in infants. It differs from lactose intolerance (extremely rare in newborns: all infants produce lactase) by these signs: blood in stools (eosinophilic colitis), widespread eczema, severe reflux, intense irritability, poor growth. It's not bloating and gas (more typical of lactose intolerance in adults). If you suspect CMPA: talk to your pediatrician who will evaluate maternal elimination diet or hydrolyzed formula.

What to Do After an Allergic Reaction: Action Plan

After a confirmed allergic reaction: stop the offending food, consult your pediatrician within 24 hours. Your pediatrician will evaluate referral to an allergist for skin tests and/or RAST. The allergist will prescribe a management plan (elimination diet, possible auto-injectable epinephrine for severe reactions). Don't reintroduce the food without medical supervision. Inform school, daycare, grandparents, and anyone caring for your child of the management plan.