Introducing allergens to your baby: the complete and safe guide

Step 1 — Choose the right moment

Introduce a new allergen early in the day (morning or lunchtime), never in the evening or before bedtime — this allows you to observe your baby for 2 hours after ingestion.

Choose a day without pressing commitments, when you are free to watch your baby.

Do not introduce several allergens on the same day — only one at a time.

Wait until your baby is in good health (no fever, no active eczema flare-up, no recent vaccination within the past 48 hours).

Step 2 — The progressive small-quantity technique

First time: offer a very small amount — the equivalent of the tip of a teaspoon (about 1–2 g). You can place the food on your baby's lip or mix it into a purée they already know.

Observe for 20 minutes: if there is no reaction, give a little more (1 full teaspoon).

Observe for a further 2 hours: watch the skin, lips, and behaviour.

If all is well, you can gradually increase the quantities on subsequent introductions.

Step 3 — Allow an observation period between different allergens

Wait 2 to 3 days before introducing a different new allergen. This makes it easier to identify clearly which allergen caused a reaction if one occurs.

Between allergen introductions, keep giving foods that are already tolerated — regularity is essential.

Step 4 — Maintain regularity

Once an allergen is tolerated, continue including it at least 2 to 3 times a week in your baby's diet.

Do not stop a tolerated allergen — stopping can lead to a loss of tolerance and the development of an allergy.

If you are unsure how to include a food regularly, think of simple staples: plain yoghurt (cow's milk), bread or porridge (gluten), salmon purée (fish), mashed hard-boiled egg (egg).

❌ "You have to wait until baby is 1 before giving cow's milk"

✅ False! Cow's milk can be introduced from the start of weaning (4–6 months) in the form of yoghurt or cheese. Cow's milk as a main drink is not recommended before 1 year, but as a food ingredient in meals it is recommended from the very beginning.

❌ "If mum or dad is allergic, baby shouldn't eat that food"

✅ False! A parental history of allergy increases the risk but does not contraindicate introduction. Quite the contrary — early introduction is even more strongly recommended to prevent the allergy. Consult an allergist if you are concerned.

❌ "A breastfeeding mother must avoid allergens to protect her baby"

✅ False! Current recommendations do not advise any exclusion diet for a breastfeeding mother in order to prevent allergies. Breastfeeding is, on the contrary, protective thanks to the antibodies it passes on.

❌ "Once a food is tolerated, I can stop giving it"

✅ Dangerous! Stopping a tolerated allergen can lead to a loss of tolerance and the emergence of an allergy to that food. Regularity (2–3 times a week) is essential to consolidate and maintain immune tolerance.

❌ "You need to introduce allergens separately over weeks"

✅ Partially false! It is true that you should introduce allergens one at a time with 2–3 days of observation. But there is nothing to prevent a reasonably brisk pace: within 6 weeks, you can have introduced the 8 priority allergens.

❌ "Organic products are less allergenic"

✅ False! The method of cultivation (organic or conventional) does not alter the allergenic proteins in foods. An organic egg is just as allergenic as a conventional one.

At what age can you start introducing allergens to your baby?

Current recommendations (PNNS, SFP, ESPGHAN 2025) advise introducing allergens from the very start of weaning, i.e. between 4 and 6 completed months. Waiting until after 1 year is strongly discouraged: late introduction increases the risk of allergy rather than reducing it.

Do you need to see a doctor before introducing allergens?

For a low-risk baby (no family history of severe allergy, no severe eczema), no prior consultation is necessary. For a high-risk baby (severe eczema, confirmed allergy in the parents), a consultation with a paediatric allergist is recommended before introducing peanut.

In what order should allergens be introduced to your baby?

There is no strict order imposed by the guidelines. The golden rule is to introduce ONE allergen at a time, allowing 2 to 3 days of observation between each new food. Start with the allergens most common in your family's diet: egg, cow's milk, gluten, fish.

What are the signs of an allergic reaction in a baby?

Hives (raised red patches), swelling of the lips or face, vomiting, sudden diarrhoea, intense crying. In the event of throat swelling, difficulty swallowing or breathing, call emergency services immediately.

Should you keep giving an allergen once tolerance is established?

Yes, absolutely! Once an allergen is well tolerated, continue including it regularly in your baby's diet (2 to 3 times a week). Stopping consumption can lead to a loss of tolerance and the development of an allergy.

Can allergens be introduced if the baby is breastfed?

Yes, absolutely. Breastfeeding is fully compatible with allergen introduction and is even protective. There is no need to stop breastfeeding in order to start weaning.

How do you introduce peanut to a high-risk baby?

For a baby with severe eczema or a confirmed egg allergy, consult a paediatric allergist before introducing peanut. They may recommend a prior test and/or a supervised introduction. For low-risk babies, peanut can be introduced at home in the form of diluted peanut butter.

What is the difference between a food allergy and a food intolerance in babies?

A food allergy involves an immune system response that can occur rapidly and be serious. An intolerance (e.g. lactose intolerance) is a non-immune digestive reaction, generally less severe and with a more gradual onset. If in doubt, consult your paediatrician.

And what about you — how did introducing allergens go with your baby? Did you have any worries? Share your experience in the comments — your story can help other parents take the plunge with confidence!