Introducing Allergens to Baby: The New Guidelines
If your parents told you to wait until age 1 or 2 to introduce peanuts, eggs, and fish, that advice is outdated. Current research (including the landmark LEAP study) shows that early introduction of allergens, starting around 4 to 6 months, actually reduces the risk of developing food allergies. The guidelines flipped.
The Big 9 Allergens
These are the foods most likely to cause allergic reactions: peanuts, tree nuts, eggs, milk (dairy), wheat, soy, fish, shellfish, and sesame. In 2023, sesame was officially added to the list and must be labeled on packaged foods.
When to Start
Most pediatricians recommend introducing allergens when baby starts solids, typically around 6 months (some say 4 months with pediatrician guidance). The key is introducing them early and consistently, not just once.
How to Introduce
**One allergen at a time.** Introduce one new allergen every 3 to 5 days. This way, if there's a reaction, you'll know which food caused it.
**Start small.** A tiny amount first. For peanuts: mix 1/2 teaspoon of peanut butter powder (like PBfit) into baby's cereal, yogurt, or puree. Don't give whole peanut butter on a spoon to a baby, it's a choking hazard.
**Morning is best.** Introduce new allergens earlier in the day so you can monitor for reactions during waking hours. Don't try a new allergen for the first time right before bed.
**Keep feeding it regularly.** One exposure isn't enough. Feed the allergen 2 to 3 times per week to maintain tolerance. This is the part most parents miss. Introducing peanut once and then not offering it again for months doesn't provide the protection.
How to Introduce Each Allergen
**Peanut:** Mix smooth peanut butter with warm water or breast milk to thin it, or use peanut butter powder mixed into puree or oatmeal. Never give whole peanuts or chunky peanut butter.
**Egg:** Scrambled egg is the easiest form. Start with a small amount of well-cooked scrambled egg. Some allergists suggest starting with baked egg (in a muffin or pancake) since it's less likely to trigger a reaction.
**Dairy:** Plain whole-milk yogurt or cheese melted into puree. Cow's milk as a drink waits until 12 months, but dairy in food is fine from 6 months.
**Wheat:** Mix infant oatmeal with wheat cereal, or offer soft toast strips or small pieces of pancake.
**Soy:** Silken tofu mashed into puree, or edamame mashed.
**Fish:** Flaked, well-cooked salmon or cod mixed into puree. Soft enough that baby can gum it.
**Tree nuts:** Tree nut butter thinned with water, similar to peanut butter introduction.
**Sesame:** Tahini mixed into puree or hummus (which contains both sesame and chickpeas).
What a Reaction Looks Like
**Mild reactions** (most common): hives around the mouth, mild swelling, slight vomiting, or increased fussiness. These usually resolve on their own or with a dose of infant Benadryl (check dosing with your pediatrician beforehand).
**Severe reactions (anaphylaxis):** difficulty breathing, widespread hives, swelling of the face/tongue/throat, extreme vomiting, loss of consciousness. This is a 911 call. Anaphylaxis is rare in first-time exposures but it can happen.
High-Risk Babies
If your baby has severe eczema or an existing egg allergy, they're at higher risk for peanut allergy specifically. The AAP recommends these babies be evaluated by an allergist before peanut introduction, possibly with a blood test or skin prick test first. Your pediatrician can refer you.
The Bottom Line
Early and consistent allergen introduction is one of the most impactful things you can do to reduce allergy risk. It feels scary, especially with peanuts. But the research is strong. Talk to your pediatrician about a plan, introduce allergens during the day so you can watch for reactions, and keep offering them regularly.