How to Introduce Allergens Safely to Your Baby

A step-by-step guide to introducing common allergens to babies, following current pediatric guidelines for reducing allergy risk.

1. When to Start. Most pediatricians recommend introducing allergens between 4-6 months of age, after your baby has started eating some solid foods and can sit upright with support. The timing often aligns with when babies begin eating purees or finger foods. Some families start with single-ingredient foods for a few weeks before moving to allergens, while others introduce them alongside first foods. Both approaches can work — the key is that your baby is developmentally ready for solids and you feel prepared to watch for reactions.
2. The Big 9 Allergens. The nine most common allergens are: peanuts, tree nuts, eggs, milk, soy, wheat, fish, shellfish, and sesame. You don't need to introduce all of these at once — many families focus on the most common ones first (peanuts, eggs, dairy) and add others gradually. Peanuts often get the most attention because peanut allergies tend to be severe, but research suggests early introduction may significantly reduce the risk of developing a peanut allergy. Tree nuts, eggs, and dairy are also commonly introduced early.
3. How to Introduce Each Allergen. Start with small amounts — a tiny taste on your finger or mixed into a food your baby already eats. For peanuts, many parents use smooth peanut butter thinned with breast milk, formula, or water (whole peanuts are a choking hazard). For eggs, you might offer a small piece of scrambled egg or mix cooked egg into a puree. Introduce one new allergen at a time, waiting 3-5 days before adding another. This makes it easier to identify which food caused a reaction if one occurs. Some families keep a simple log of what they introduced and when. If your baby tolerates the allergen well, continue offering it regularly — about 2-3 times per week. Consistent exposure seems to be important for maintaining tolerance.
4. What to Watch For. Most allergic reactions in babies are mild and appear within minutes to a few hours of eating. Common signs include hives or rash around the mouth, vomiting, diarrhea, or unusual fussiness. More concerning signs include difficulty breathing, widespread hives, swelling of the face or lips, or extreme lethargy. Many babies develop a mild rash around their mouth when trying new foods — this isn't always an allergic reaction. It could be irritation from acidic foods or just sensitivity to new textures. When in doubt, stop the food and consult your pediatrician. If you notice any concerning symptoms, stop offering that food and contact your pediatrician. For severe reactions like difficulty breathing or widespread swelling, call 911.
5. Special Considerations. If your baby has severe eczema or an existing food allergy, your pediatrician might recommend introducing allergens under medical supervision. Some doctors suggest allergy testing before introduction in these cases, though this isn't always necessary. If you have a family history of severe food allergies, discuss your approach with your pediatrician. They might recommend specific timing or methods, but family history alone doesn't usually mean avoiding allergen introduction. Some parents feel more comfortable introducing allergens when their pediatrician's office is open, rather than on weekends or evenings, in case they need guidance about a reaction.