The guidelines have completely flipped. If you had a baby 15 years ago, you were told to delay peanuts until age 3. Now the evidence says the opposite: introducing allergens early — as early as 4-6 months — actually reduces the risk of developing food allergies. Here's exactly how to do it safely.
Why early introduction works
The landmark LEAP study (Learning Early About Peanut Allergy) published in 2015 changed everything. It found that babies who ate peanut products regularly starting at 4-11 months had an 81% lower risk of developing peanut allergy by age 5 compared to babies who avoided peanuts. The follow-up EAT study extended this principle to other major allergens.
The science behind it: early exposure trains the immune system to recognize food proteins as safe rather than threatening. Think of it as introducing your baby's immune system to peanuts when it's still flexible and learning, rather than waiting until it's already decided peanuts are the enemy.
When to start
Begin introducing allergens when your baby is ready for solid foods, typically around 4-6 months. Signs of readiness: good head control, sitting with support, showing interest in food, and the tongue-thrust reflex has diminished. You don't need to wait until after non-allergenic foods are established — you can introduce allergens alongside other first foods.
The top allergens and how to introduce them
Peanut
Never give whole peanuts or peanut butter by the spoon — they're choking hazards. Mix a small amount of smooth peanut butter or peanut powder (like PBfit) with breast milk, formula, or pureed fruit until it's thin and smooth. Start with about 1/4 teaspoon worth of peanut protein.
Egg
Scramble an egg well-done and puree or mash it with breast milk or formula. Or mix hard-boiled egg yolk into a puree. Start with the whole egg — the protein that causes reactions is primarily in the white, and introducing both together is fine.
Cow's milk (as ingredient)
Not as a drink until 12 months, but as an ingredient starting at 4-6 months. Yogurt, cheese, milk mixed into purees — all fine. Full-fat plain yogurt is one of the easiest first introductions.
Tree nuts, wheat, soy, fish, shellfish, sesame
Thin nut butter mixed into purees (never whole nuts). Soft well-cooked pasta or infant cereal for wheat. Soft tofu for soy. Well-cooked, pureed or flaked fish. Tahini mixed into hummus or purees for sesame. Each can be introduced the same way: small amount, mixed into a familiar food.
The safe introduction protocol
Step 1: Introduce one new allergen at a time. Step 2: Start with a very small amount — a taste on the lip or a tiny bit mixed into food. Step 3: Wait 10 minutes. If no reaction, give a slightly larger serving. Step 4: Watch for 2 hours after the full serving. Step 5: Introduce the next allergen on a different day.
Do introductions at home (not at daycare or a restaurant) during a time when you can observe your baby for a couple of hours. Morning or midday is ideal — not right before bedtime. Have infant-appropriate antihistamine dosing information ready, though you likely won't need it.
What a reaction looks like
Mild reactions (manage at home, call pediatrician): A few hives around the mouth, mild redness or swelling at the contact area, slight fussiness or one episode of vomiting. Severe reactions — call 911: Widespread hives or swelling, difficulty breathing or wheezing, persistent vomiting, lethargy or limpness, swelling of the tongue or throat.
Severe reactions on first exposure are rare but possible. This is why you introduce at home and watch carefully. If your baby has a mild reaction, don't re-introduce that food on your own — get guidance from an allergist.
The critical part most parents miss: keep going
Introduction alone isn't enough. Research shows you need to keep giving allergenic foods regularly — at least 2-3 times per week — to maintain tolerance. A single introduction followed by months of avoidance doesn't provide lasting protection. Make peanut butter on toast, scrambled eggs, yogurt, and fish regular parts of your baby's diet after successful introduction.
Early allergen introduction is one of the few evidence-based things you can do to genuinely reduce your child's risk of a lifelong condition. It feels scary, but the science is strong. Start early, go slowly, and keep those allergens in regular rotation.