The introduction of allergenic foods is one of the most anxiety-inducing milestones of the first year for allergy-conscious parents. But the guidance has changed dramatically in the last decade — and in a direction that should be reassuring. Here's the current evidence on when and how to introduce the top allergens, and why waiting is no longer recommended.
The Evidence That Changed Everything
Until around 2010, the standard guidance was to delay introduction of highly allergenic foods — peanuts, eggs, tree nuts, fish — until 12 months or beyond. The logic was that a baby's immune system needed time to mature before encountering potential allergens.
The LEAP (Learning Early About Peanut allergy) trial, published in 2015, turned this guidance upside down. In this landmark randomised controlled trial, babies at high risk for peanut allergy who were fed peanuts regularly from 4–6 months had an 80% reduction in peanut allergy by age 5 compared to those who avoided peanuts. The protective effect of early introduction was dramatic and consistent.
Subsequent research (LEAP-On, EAT study, and many others) confirmed the finding across multiple allergens: early, regular introduction of allergenic foods in the first year of life is protective rather than risky. The immune system, when exposed to allergens during a window of tolerance in early life, is more likely to develop tolerance than sensitisation.
Current Guidelines
The AAP updated its guidelines in 2019 to reflect the LEAP evidence:
- For all babies: no need to delay introduction of any allergen beyond when solids are otherwise introduced (around 6 months)
- For high-risk babies (severe eczema or known egg allergy): discuss timing with a pediatrician before peanut introduction; some may benefit from allergy testing first
- Early introduction is actively beneficial, not just neutral
The UK equivalent guidance (from the British Society for Allergy and Clinical Immunology) aligns: introduce allergenic foods from around 6 months regardless of family history.
The Top 9 Allergens
These are the foods responsible for the vast majority of food allergic reactions:
- Peanuts
- Tree nuts (cashew, almond, walnut, pistachio, etc.)
- Eggs
- Cow's milk (as a direct food; formula and breastmilk already expose to cow's milk protein)
- Wheat
- Soy
- Fish
- Shellfish
- Sesame (added in 2023 in the US)
How to Introduce Allergens Safely
The Protocol
- Introduce one new allergen at a time: This allows you to identify the cause if a reaction occurs. Wait 3–5 days between new allergens.
- Introduce in the morning: So you can observe baby for several hours afterward. Never introduce a new allergen just before bedtime or a nap.
- Start with a small amount: A tiny portion (a quarter teaspoon or less) for the first introduction.
- Increase gradually: If no reaction after the first introduction, increase the amount over subsequent days.
- Offer regularly once introduced: The protective effect requires regular, ongoing exposure — approximately 3 times per week. An allergen introduced once and then avoided doesn't confer protection.
Safe Forms for Each Major Allergen
- Peanut: Smooth peanut butter thinned with water or breastmilk (never whole peanuts — choking hazard). Or peanut puffs designed for infants. Never chunky or whole nuts.
- Egg: Well-cooked scrambled egg or hard-boiled egg mashed. Fully cooked first — lightly cooked egg is more allergenic than fully cooked.
- Tree nuts: Finely ground or as smooth nut butter thinned with water. Cashew and almond butters are widely available. Never whole nuts.
- Fish: Flaked, well-cooked, deboned. Salmon is a good starting point — soft, nutritious, widely available.
- Wheat: Well-cooked soft pasta or bread. Most babies have already encountered wheat through formula or purees by this point.
- Dairy: Yogurt or small pieces of soft cheese. Cow's milk as a drink before 12 months is not recommended, but dairy in foods is appropriate.
- Sesame: Tahini thinned with water, or hummus.
Recognising an Allergic Reaction
Most reactions to first introductions are mild. Know what to watch for:
Mild reactions (monitor, contact pediatrician if concerned):
- Hives (raised, itchy welts) around the mouth or body
- Mild redness or swelling around the mouth
- Runny nose, watery eyes
- Mild vomiting or diarrhoea
Severe reaction (anaphylaxis) — call 911 immediately:
- Difficulty breathing, noisy breathing, or stridor
- Swelling of the lips, tongue, or throat
- Pale or blue skin
- Sudden extreme distress or limpness
- Loss of consciousness
Anaphylaxis typically develops within 15–30 minutes of ingestion. Staying with baby and observing for at least an hour after each new allergen introduction is recommended.
If Baby Has Eczema: Higher Vigilance
Eczema, particularly moderate to severe eczema in the first months of life, is the strongest risk factor for food allergy. The skin barrier disruption in eczematous skin allows allergen sensitisation through skin contact rather than oral exposure — this is why keeping eczema well-controlled and avoiding allergen exposure on broken skin (no peanut butter in the bath) matters.
For babies with moderate to severe eczema, discuss allergen introduction with your pediatrician or allergist before starting, particularly for peanuts and eggs. Some may be recommended for testing before oral introduction.
For the full context on starting solids, see our first foods guide, our BLW guide, and our finger foods guide.