Food allergies affect a significant portion of the population, with adverse reactions ranging from mild discomfort to life-threatening conditions. Understanding the most common food allergens and how to introduce them safely is crucial for parents and caregivers. This article aims to provide valuable insights into the most prevalent food allergens, recommendations for introducing allergenic foods, and the signs of allergic reactions to look out for.

Common food allergens and introduction strategies

What are the most common food allergens?

The most common food allergens are egg, cow’s milk (dairy), peanuts, tree nuts, soy, sesame, fish, shellfish, and wheat.

When do I introduce allergens?

Growing evidence suggests that delaying the introduction of allergens may increase the risk of allergies in children. The current recommendations are to start solids at around 6 months of age and not before 4 months. Once your baby has commenced solids you can introduce allergenic foods. Aim to introduce all allergenic foods before their first birthday.

How do I introduce allergens?

• It is recommended to give one allergen at a time when first introducing new foods. This way the causative food can be easily identified if your baby has a reaction.
• Ideally, when introducing allergens, they should be given earlier in the day (not right before bedtime) and in a location where medical assistance is available if needed (not when travelling in remote locations).
• A cautious approach is to start with a small amount e.g., ¼ teaspoon and gradually increase the amount over 5 days. This is most easily and reliably achieved by mixing an allergen with other foods in puree or very soft form and directly spoon feeding your baby.
• Do not rub allergens onto your baby’s skin or outside their mouth when first introducing new foods. If infants are exposed to allergens through their skin, they are at increased risk of having an allergic reaction when they are given that food by mouth later. For this reason, we recommend avoiding skincare products containing food products such as nut oils in young babies who are not eating these foods yet. This is particularly important for babies with eczema. If your baby has eczema or you find it difficult to avoid getting food on the outside of your baby’s mouth you can apply a barrier cream around their mouth and on areas of their face which may contact the allergenic food. Once your baby has tolerated the allergenic food a few times and is regularly ingesting that food then skin contact is ok.
• Ideally all the allergens should be introduced prior to 12 months age. Once your baby is tolerating an allergen, they should continue to eat it on a regular basis, ideally twice per week.

Examples of first allergenic foods

Peanuts

Smooth peanut butter (thinned with a little water, breastmilk or formula or mixed with other purees). Read this article on when to introduce nuts.

Tree nuts

Most of the tree nuts are available as a butter or finely ground (flour or meal). The tree nuts include almonds, brazil nuts, cashew nuts, hazelnuts, macadamias, pecans, pistachios and walnuts. Choose smooth nut butters that can be thinned with a little water, breastmilk or formula or mixed with other purees).

Sesame

Tahini (thinned with a little water, breastmilk or formula or mixed with other purees) or hummus, which contains tahini.

Eggs

Hard boiled, scrambled or omelette.

Cow’s milk

Yoghurt, ricotta, cottage cheese. Most standard formulas are cow’s milk-based. You can add plain cow’s milk to cereal, but it should not be a main drink before 12 months of age.

Wheat

Couscous mixed with vegetable puree, semolina porridge, iron-fortified wheat-based cereals prepared with breastmilk or formula.

Soy

Mashed silken tofu mixed with puree, soy yoghurt or soy milk.

Shellfish

Cooked prawns or crab pureed with avocado or vegetables.

Fish

De-boned and finely flaked cooked salmon or white fish or tinned tuna mixed with puree.

What does an allergic reaction look like?

Immediate Allergies

Signs of an allergic reaction include hives, flushed skin, swelling of the eyes, lips or face, noisy or difficulty breathing, a hoarse cry or voice, vomiting, lethargy or changes in behaviour.

Most immediate type allergic reactions will occur within minutes and up to 2 hours later. If your baby has signs of an allergic reaction seek medical assistance and do not give the suspected food allergen again until advised to do so by an experienced health professional.

Call an ambulance immediately if your baby becomes pale or floppy, has noisy or laboured breathing, has tongue or mouth swelling or any other serious concerns. Anaphylaxis is a severe, potentially life-threatening allergic reaction which requires immediate medical attention.

Delayed Allergies

Some other types of allergies e.g. ‘FPIES’ (Food Protein Induced Enterocolitis) have a more delayed onset and can present several hours later with symptoms including profuse vomiting, pallor, floppiness, lethargy and diarrhoea.

There should not be any hives, facial swelling or difficulty breathing. These reactions may not occur until the baby has been given the food a few times and can occur with almost any food including seemingly harmless foods such as rice, sweet potatoes, oats, bananas.

It is important to seek medical attention as some children will require medication or intravenous fluids depending on the severity of their reaction. A paediatrician or allergist should be involved to confirm the diagnosis.

Management includes avoiding the trigger foods. Most children will only be allergic to one food but for some may need to avoid multiple foods. Reintroduction of the trigger food is done under the guidance of a paediatric allergist. Most children with FPIES grow out of it by the time they are 3 years old, but for some it will be much earlier or later than this.

Special considerations

It is important to note that if your child has a reaction to one food, you should still continue to offer all other foods they have previously tolerated. For example, if they tolerate peanuts but later have a reaction to cashew then only stop cashew.

This information is intended as general advice only. If your child has eczema, there is a strong family history of allergies, or you have other concerns, always consult a health professional for further advice.