Lucy Jackman, The Happy Tummy Dietitian, has a private practice, and works in a world renowned NHS children’s hospital based in Central London, where she specialise in gastroenterology and food allergy. This is Lucy's deep dive into Allergens, how, why and crucially how to maintain accepted allergens in your little one's diet.

Introducing allergens

For most parents I speak too, the introduction of allergens is probably the scariest part of weaning. We see sad media stories where a child has had a severe allergic reaction and passed away. This of course, can happen but please be assured that these types of reactions are are extremely rare!

Over the years the advice about allergen introduction has changed and this is because research has improved our understanding. We now have evidence and research that shows that early introduction of allergens, especially peanut and egg, is protective for allergies! So when and how you introduce these allergens into your little one’s diet in weaning and beyond, can prevent an allergy from happening! How amazing is that!? 

Of course there is a potential to be allergic to any food, but this is unlikely.  In the UK there are 14 “top” allergens; celery, cereals containing gluten (wheat, barley and oats), crustaceans (such as prawns, crab and lobster), eggs, fish, lupin, milk, molluscs (such as mussels and oysters), mustard, peanuts, sesame, soybeans, sulphur dioxide and sulphites and tree nuts (such as almonds, hazelnuts, walnuts, Brazil nuts, cashews, pecans, pistachios and macadamia nuts). In clinical practice, we are seeing a emerging trend of pea, lentil and coconut allergies becoming more prevalent – but at the moment, these are still not considered a common allergen. 

Should all children introduce allergens early?

For all children who are starting solids, we would recommend not delaying the introduction of allergens, this means ideally not later than 7 – 8 months in most cases. However there are some children who are higher risk of allergy; so they have eczema, they have another food allergy already or there is a family history of atopy (which means asthma, eczema, hayfever and food allergy), in these children we actively want to put the allergens in early, so from 4 – 6 months if developmentally ready

How should I introduce the allergens?

After the initial stages of weaning, so your little one is comfortable with taking solids, is the ideal time to start offering allergens. The first priority foods should be peanut and egg, this is what we have research on specifically for allergy prevention.

Key thing to make sure, is that before you start your little one is well, so no coughs, colds or nasty illnesses brewing. If they have eczema, ensure this is managed and well controlled before you start.  If all is well, you are good to go!

• Offer one allergen at a time. This is super important, because if your little one were to have a reaction and you had given two new allergens at a time, you would not know which had caused that reaction. 

• Start slow and build up. I often recommend using spoon measures that you might use when baking, this helps know exactly how much you are giving.  The amount is gradually built up over the coming days, usually doubling up the portion each time. So from ¼ teaspoon to ½ teaspoon, from ½ teaspoon to a whole teaspoon and so on. You can increase daily or leave a day or 2 between each increase – this will vary depending on the food. For example a food like wheat is more likely to trigger a delayed reaction (if any), so leaving time between increased doses can be helpful to unpick this. 

• Offer the allergen early in the day. This is just helpful as it gives you lots of time to monitor your little one

• The allergen can be mixed into something your little one has already eaten and tolerated without issue. So maybe some banana puree with peanut butter mixed in for example 

If you don’t eat some of the common allergens as a family and these will not feature in your little one’s diet regularly, its usually advised not to just try once and then not give again. Prioritize the ones that will be their usual diet.

How do I know if they have reacted?

First off, as I said above, severe immediate food reactions are extremely rare in weaning age. There are of course some key symptoms to look out for.  Maybe first, its helpful for me to explain different types of food allergy (they are not all the same) and food intolerance (again not the same thing)!

Food allergy is an immune mediated reaction to a food. The immune systems function is to keep us safe from harmful bugs, viruses, etc but sometimes it gets it not quite right and thinks that something like a food protein is a threat, this triggers a few different responses in the body that ultimately leads to an allergic reaction. Too make it a little more confusing, there is 2 types of reactions that can occur:

1. An IgE mediated reaction, also known as an immediate reaction. These reactions usually trigger symptoms as soon as the food is eaten or by 2 hours. This is the type of allergy that can (possibly) cause an anaphylaxis. 

2. A non-IgE mediated reaction, also known as a delayed reaction.  These usually trigger symptoms much slower, so after 2 hours but they can be up to 72 hours after the food is eaten! 

It’s possible that reactions happen the first time your little one eats a food but usually its on a later exposure we see the reaction occur. On the initial exposure, the body has become sensitized (so a bit twitchy to that allergen but still making its mind up), then the next exposure, they body decides “nah we don’t want this” and triggers a reaction.

Remember, severe life-threatening allergic reactions are very rare in weaning age!

Now intolerance! Delayed food allergies and food intolerance often get used interchangeably, but these are not the same thing (hence the different names)! In a food intolerance, the body has difficulty in digesting a food, usually because there is something like an enzyme lacking or not functioning as it should. There is no immune system involvement, like there is in food allergy

We now know the difference between the 2 types of food allergies, but the key thing when weaning is to be aware of what the possible symptoms are! Allergic reactions can involve 2 main systems in the body: The respiratory (lungs and breathing), the skin and the gut (tummy)

If you think your little one has had an allergic reaction, you should discuss with a health care professional, weather it be immediate or delayed. For immediate reactions, seek medical attention immediately. If your little one has any symptoms of anaphylaxis – shortness of breath, tongue swelling, difficulty breathing, becoming floppy / unresponsive – they must be taken to hospital immediately, call 999 without delay

I have tried the allergen, all is fine, what should I do now?

Yay! You have tried the allergen and its been absolutely fine! Now the next step is super important, so listen up! You now need to keep that allergen in the diet regularly, ideally 2 – 3 times per week until your little one is around 5 years old. This helps the body to keep recognising that allergen, so it remains familiar. Don’t worry too much about quantity and ticking off a weekly list if the allergen has been given enough times, the key thing is that its regularly in the diet

This might sound near impossible as there are a lot of allergens, but below are some helpful ways to keep allergens in the diet

For the nuts, it can be really helpful, once you have tried a variety, to buy a mixed bag, blend it up in a coffee grinder and sprinkle on meals (usually breakie) where you can!

Its super exciting that you can help reduce your little ones allergy risk by getting these foods in early in weaning, it can be scary, of course, but severe reactions are very very rare (as I have mentioned  a few times already 😉