Allergen advice for weaning

Baby eating vegetables

Reviewed on 06.12.2022 by Helen Farnsworth, Nutritionist

Like it or not, allergies are a fact of life. In the UK, 40% of children have been diagnosed with an allergy. The four most common allergies in children are food allergy, eczema, asthma, and hay fever. (Allergy UK)

Some allergies (including food allergies) have a genetic link. This means that the tendency to have an allergy can be passed down from parent to child. If anyone in your immediate family has an allergic condition such as asthma, eczema, hayfever or food allergies, your baby is more likely to have an allergy, too.

Of course, allergies aren't the end of the world, and your baby may very well not develop any at all - but if there is a history of allergy in the family, it makes sense to take a bit of extra care during weaning. Weaning with allergy concerns

Allergenic foods such as milk, eggs, wheat, gluten, soya, fish, shellfish, peanuts, tree nuts, seeds can be introduced once you have started weaning your baby; there is no evidence to support delaying introduction of these foods beyond 6 months.

However, if your baby already has a diagnosed food allergy or eczema, or if you have a family history of food allergies, eczema, asthma or hay fever, you may need to be particularly careful when introducing foods, so talk to your GP or health visitor first.

A good tip (especially once you start to introduce some of the high allergy risk foods) is to introduce each allergen on its own in small amounts, adding a new food every other day so that you can watch carefully for any signs of an allergy. Make sure your child is well at the time of allergen introduction, i.e. not when they have a temperature, just had a vaccination, or have a cough or a cold.

This way, if you see any symptoms, you can be fairly sure which food is the culprit. Once you're sure a food is safe, keep offering it as part of your baby’s usual diet.

By the age of 12 months at the latest, your baby should have been introduced to all the major allergenic foods (where appropriate).


Allergies and intolerances may seem similar, but they're actually quite different.

The table below will help explain the main differences between food allergies and intolerances. (Important note: this information is intended as advice only; if you think your child may have a food allergy or intolerance, you should always contact your health visitor or GP for more information.)


Food allergyFood intolerance
What is it?An adverse immune response to a specific protein within a food.An adverse bodily response to a component within a food (not necessarily a protein) with no immune involvement.
Common or rare?Rare, but risk is higher in families with a history of allergy.More common than an allergy, but still unusual in children.
What causes it?The immune system thinks the protein in the food is harmful and reacts to it, causing symptoms (see below).There are a number of causes; sometimes a lack of enzymes means food can’t get digested, or sometimes foods can cause symptoms on their own.
AmountsA reaction can be caused by the smallest traces of the food.Usually a reaction only happens after consuming at least a teaspoon of the food.
SymptomsDiarrhoea, Vomiting, redness, swelling, difficulty breathing, skin reactions including itching or urticaria (hives) and anaphylaxis, among others.Headache, bloating, stomach ache, diarrhoea, sickness. No anaphylaxis.

Tests for allergies and intolerances


If you are worried that your little one has a food allergy, there are a few types of test that your GP or allergy specialist may suggest.

  • Skin prick test (SPT) – During this test, an allergist will place drops of solutions containing different potential allergens on the skin, then use a tiny lancet to prick through the solution and into the top layers of the skin. A few minutes later, the allergist will check to see whether the skin has reacted by swelling or turning red; this shows a specific type of allergy called an ‘IgE allergy’.
  • Blood tests (RAST or ‘specific IgE’ test) – This involves taking a blood sample and counting the number of ‘IgE’ antibodies it produces in response to the suspect food.
  • Food challenge – In this test, the allergist will place very small amounts of the suspect food in your baby's mouth and observe any symptoms (under medical supervision).
  • Food exclusion and reintroduction – This 'test' involves removing the suspect food from your baby's diet to see what effect this has on symptoms. If the symptoms improve, then your doctor may suggest re-introducing the food briefly to see if the symptoms return.

High street tests

There are allergy tests available commercially, but many of these high street tests are expensive and are based on complementary and alternative medicine and aren't supported by any scientific evidence:

  • ‘IgG’ blood test
  • Kinesiology (muscle testing)
  • Hair analysis
  • Leucocytotoxic test
  • VEGA/Electrodermal test

If you would like to get NHS-approved allergy testing done privately, Allergy UK has a list of accredited specialists who can help.


Any food containing protein has the potential to trigger an allergy; however, some are more common culprits than others, including peanuts, tree nuts, fish and shellfish, cow’s milk, eggs, soya, wheat, and some fruits and vegetables.. Allergic reactions happen when the body mistakes the proteins for harmful invaders and tries to attack them.


We don't really know what makes a food likely to cause intolerance; however, lactose, a milk sugar, is the most common offender. Lactose-intolerant people produce less of the enzyme the body needs to break down lactose, which can lead to uncomfortable symptoms.


Anaphylaxis is a type of allergic reaction that affects the whole body and can be life-threatening. Thankfully, it is very rare; however, if it occurs it requires immediate medical treatment, which is why all allergies should be taken seriously.

Anaphylaxis usually occurs within a few minutes of exposure to the allergen, but can take a few hours to develop. The symptoms vary, but might include skin redness, urticaria (hives) appearing on the body, itching or swelling in the mouth and throat, difficulty in swallowing or speaking, a rapid heartbeat, wheezing or worsening of asthma, feeling sick or vomiting, a drop in blood pressure (the person may feel weak or fall down) and unconsciousness.

f you believe that your child may be experiencing anaphylaxis, call 999. Usually anaphylaxis is treated with injectable adrenaline (an EpiPen), and some people who have had anaphylaxis in the past carry this with them just in case.

If you suspect that your child may have an abnormal reaction to a food, it's important to discuss it with your GP. Sometimes what looks like an allergy or an intolerance might be something different, so you don’t want to take things out of your child’s diet until you're certain of the cause.

If the symptoms were obviously related to one specific food (for example, an egg) then it may be wise to avoid giving your child egg until you have a chance to speak to the GP. Even if you do this and the symptoms stop, you should still book an appointment to see your GP so you can have your concerns confirmed and properly diagnosed.

It may help you to write down what your child ate and exactly what happened so that you don’t forget anything that may be important when you see your doctor; this will also help them to make the right diagnosis.

Your GP may want to do a skin prick test (SPT) or a blood test (called a RAST). Sometimes they might ask you to remove that food from your child's diet to see if symptoms go away, and then add it back in (under medical supervision) to see if symptoms return.

Egg allergy in children


Eggs are one of the most common foods to trigger an allergic reaction in babies and young children. Most children with an egg allergy will start to outgrow it by the time they go to school but in some it will persist into later childhood or in rare cases, adulthood Reactions to egg are usually triggered by the protein part of the egg (mainly in the egg white), but they can also occur from other An egg allergy can be to all forms of egg, or just eggs which aren’t thoroughly cooked.

What do you need to avoid?

Eggs on their own are fairly easy to avoid, but don't forget that eggs are also found in lots of different products.

In the UK and EU, all of the 14 common allergens, of which egg is one, must be listed and highlighted (usually in bold) within the ingredients list on all prepacked food products. Example of a food label:

INGREDIENTS: Rapeseed Oil (78%), Water, Pasteurised Free Range Egg & Egg Yolk (7.9%), Spirit Vinegar, Salt, Sugar, Sunflower Oil, Lemon Juice Concentrate, Antioxidant (Calcium Disodium EDTA), Flavourings, Paprika Extract

Outside of the EU food labelling laws may be different, so it is important to check ingredients carefully, especially when eating out whilst on holiday.

Allergen information must also be provided for ‘non prepacked’ foods, (e.g. when eating out), so it’s important to highlight your egg allergy request when ordering food.

Most manufacturers and supermarkets can give you a list of egg-free foods on request; however, product formulations do change, so it's important to check the label as well. All foods that are labelled “suitable for vegans” will also be egg-free. You can also buy egg-replacers to use in home cooking.

Peanut allergy

According to latest figures from Allergy UK, peanut allergy affects around 1 in 50 children in the UK. It usually develops in early childhood but, occasionally, can appear in later life. For about 1 in 5 children, peanut allergy will resolve itself, usually by the age of about 10 years old; however, many people have peanut allergy for life.

Peanuts are part of the ‘legume’ family, which includes beans and peas, and are different to ‘tree nuts’ like walnuts and hazelnuts. Approximately 30-40% of children with peanut allergy will have an allergy to at least one tree nut.

What do you need to avoid?

All peanuts and peanut-containing products, e.g. peanut butter, peanut spread, peanut sauces, peanut flour and peanut oil, and any product containing peanut as an ingredient.

As for egg, In the UK and EU by law, peanut is another of the 14 common allergens that must be listed and highlighted (usually in bold) within the ingredients list on all prepacked food products on any product with an ingredients list.

Example of a food label: INGREDIENTS: Maize, Sugar, Peanuts (7.5%), Barley Malt Flavouring, Molasses, Honey (1%), Salt, Vitamins & Minerals: Niacin, Iron, Vitamin B6, Vitamin B2 (Riboflavin), Vitamin B1 (Thiamin), Folic Acid, Vitamin B12

Outside of the EU food labelling laws may be different, so it is important to check ingredients carefully, especially when eating out whilst on holiday.

Allergen information must also be provided for ‘non prepacked’ foods, (e.g. when eating out), so it’s important to highlight your peanut allergy request when ordering food.

You may also see some precautionary labelling of food products, where there is a risk that the food may have come into contact with peanuts during the manufacturing process. Products such as these will usually be labelled as ‘May contain peanuts’ or ‘Made in a factory containing peanuts’. It is safest to also avoid foods with “may contain” warnings in the case of a peanut allergy.