Infant feeding and the timely introduction of food allergens

We now know that this strategy makes food allergy less likely, but families need guidance.

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Australia’s  prevalence of early childhood food allergy is one of the highest in the world, with one in 10 infants diagnosed with a food allergy by one year of age [1].

Hospital presentations for anaphylaxis have increased for all age groups in the past three decades and food remains the major cause of anaphylaxis in the 0-4 age group [2].

We now know that introducing the common food allergens into an infant’s diet in the first year of life can reduce the likelihood of food allergy developing. But families need guidance and reassurance with the early introduction of allergens. Medical practitioners can assist by directing them to evidence-based resources, including practical information about how to introduce the common food allergens and how to optimally manage eczema where required.

The natural history of food allergy shows that allergy to cow’s milk, egg, soy and wheat usually resolves through childhood and adolescence, with around 80% outgrowing their food allergy [2,3]. However, 80% of children with peanut, tree nut, shellfish, fish or sesame allergy remain allergic through to adulthood [4,5].

The rise in allergic diseases, such as food allergy and eczema, is not well understood, but is thought to be a complex interplay between Western lifestyle, the environment and genetic predisposition. Infants with a family history of allergic disease are at higher risk, but infants with no family history can also develop allergies.

There are a number of proposed theories on the causes of food allergy development.

These include:

1. The delayed the introduction of major allergens, particularly peanut and egg: Recent studies have shown that introduction of common food allergens (e.g. peanut, egg) to babies after 12 months of age can increase the chance of developing food allergies [6].

2. Skin exposure to allergens: There is evidence that the use of moisturisers or creams containing food protein (e.g. nut, dairy, oat) in infants with eczema and who have a damaged skin barrier may lead to development of food allergy. This low dose exposure can sensitise infants through the skin rather than through the gut, increasing their risk of developing a food allergy [7].

3. The hygiene hypothesis: This suggests that less exposure to endotoxins in early childhood is associated with an increased risk of allergy. It is thought that early exposure to microbes and their products helps the immune system’s ability to tell the difference between harmful and harmless substances. Further research shows that the type of bacteria that the mother and infant are exposed to may alter the risk of developing allergic disease [8].

4. Vitamin D deficiency: Vitamin D is important for a healthy immune system. A deficiency in Vitamin D (via reduced sun exposure) has been linked to a higher risk of allergy [9]. Studies have shown that countries further from the equator have higher hospital admission rates for allergic reactions in children. In addition, infants born in the autumn and winter months have a higher incidence of food allergy.

5. Food processing methods: It is known that roasted peanuts are more allergenic than boiled peanuts. Peanut allergy is higher in countries such as Australia and the US where peanuts are roasted compared with Asia, where peanuts are boiled [10].

In 2008, Australasian Society of Clinical Immunology and Allergy (ASCIA) changed their infant feeding and allergy prevention guidelines to encourage parents to introduce common food allergens at the same time as they introduce other foods (that is, do not delay introduction). Despite this, parents have remained reluctant due to fear their baby would have an allergic reaction.  

After the landmark Learning Early About Peanut (LEAP) study was published, ASCIA strengthened their guidelines (in 2016), recommending that common food allergens, including peanut and egg, be introduced during the first year of life, preferably around six months (not before four months) [11]. The ASCIA guidelines are relevant to all infants, including those thought to be at high risk, which is defined as the child having eczema and/or siblings or parents with allergic disease.

To assist with the implementation of the updated ASCIA guidelines, the National Allergy Strategy, supported by the Australian Government, launched the Food Allergy Prevention Project in 2018.

The Nip Allergies in the Bub website [12] was developed to provide parents with practical information about how to introduce the common food allergens and how to optimise eczema management.  A phone service with trained staff is also available to provide further support to parents. In addition, the website includes information and education resources for health professionals including resources to provide to parents.

Results of an Australian SmartStartAllergy study [13], a novel tool that contacts parents via their general practice to identify whether peanut had been introduced by 12 months of age, showed that the parent-reported rates of allergic reactions were similar to that in the HealthNuts [14] cohort conducted before the early introduction guidelines were introduced.

However, it is important to note that the reported rates in the SmartStartAllergy cohort are parent-reported rates (and therefore an overestimation), whereas the HealthNuts’ figures are derived from food challenges.  Preliminary SmartStartAllergy data indicate that most parents have introduced peanut to their baby by 12 months of age, indicating that parents are adhering to the updated ASCIA guidelines.

What is the evidence for timely introduction of food allergens?

Introducing peanut before 12 months of age has been demonstrated to significantly reduce the risk of peanut allergy in high risk infants [6].

In 2015, the LEAP study was published, which provided evidence that the early introduction of peanut in high-risk infants (those with moderate to severe eczema +/- egg allergy) provided an 80% reduction in the development of peanut allergy. Further randomised controlled trials have also shown the benefit in the timely introduction of cooked egg. However, there are currently few studies that have examined other major food allergens.

Cohort studies have suggested an association between delayed introduction of common allergenic foods such as wheat, cow’s milk and fish with a higher incidence of food allergy; however, further evidence is required to clarify optimal timing for the introduction of these foods [15]. In addition, breastfeeding when solid foods are first introduced may help reduce the risk of infant allergies, although evidence for this is weak [16].

When to introduce common food allergens

Introducing the common food allergens (peanut, tree nuts, cow’s milk, egg, wheat, soy, sesame, fish and shellfish), in the first year of life can reduce the likelihood of the development of food allergy.

Solid foods should be introduced to the infant around six months, but not before four months, when the infant is developmentally ready.

How to introduce food

A variety of solids should be introduced, starting with iron rich foods. All infants, including those at high risk, should be given the common food allergens unless they are already allergic to the food.

It is important that peanut and tree nuts are in the form of a smooth paste or a nut flour to avoid choking and that egg is well cooked (e.g. hard boiled). Heating modifies the protein in egg, making it less allergenic if well cooked, however this is not the case for all common food allergens.

Breastfeeding should be continued where possible. Hydrolysed (both partially and extensively hydrolysed) infant formula are not recommended for the prevention of allergy [17].

When introducing food for the first time, food should never be smeared or rubbed on the infant’s skin, especially if they have eczema. This could sensitise the infant to that food, making it more likely for them to develop a food allergy. Additionally, contact skin reactions do not necessarily predict a food allergy.

One new food at a time should be introduced so it is easier to establish the trigger if an allergic reaction occurs. If the parent is anxious about food allergy, they can conduct a small trial by placing a small amount of food inside the infant’s lip. If there is no reaction after a few minutes, they can offer the child  a quarter of a  teaspoon of the allergen. The amount can be gradually increased from a half to two teaspoons over two days and then continued to include those foods (common allergens) in the infant’s diet at least twice a week to maintain tolerance.

Will a reaction happen on first ingestion?

Some infants will have a reaction despite best practice guidelines being followed. If a reaction does occur, the food trigger (allergen) should be stopped and medical advice sought. Severe reactions (anaphylaxis) in infants are uncommon.

How to manage an allergic reaction

Symptoms of an allergic reaction may be mild, moderate or severe.

Information on recognising and managing an allergic reactions can be found on the Nip Allergies in the Bub website [12].

Mild or moderate allergic reactions (swelling of the lips, eyes or face, urticaria or vomiting) can be treated using non-sedating antihistamines. If there are symptoms of anaphylaxis (difficult/noisy breathing, swollen tongue, pale/floppy) treat with adrenaline if available and call an ambulance immediately. Infants should be laid flat, not held upright. The older infant should not be permitted to stand and walk. They can be allowed to sit if breathing is difficult and placed on their side if vomiting or unconscious. If an adrenaline injector (e.g. EpiPen® Jr) is available, give immediately.  ASCIA recently changed its adrenaline injector guidelines allowing EpiPen^®Jr (0.15mg) to be prescribed for children weighing from 7.5-20kg [18].  

Sedating antihistamines should not be used in anyone if there is a risk of anaphylaxis, including children under the age of two, as drowsiness can be confused with signs of anaphylaxis [18].

Optimising eczema management

Eczema affects 15-20% infants [19] in Australia. It is important to optimise eczema management to prevent food allergy sensitisation through the skin. The skin functions as an important barrier and in the case of eczema, it is suggested that a defective skin barrier allows allergens to penetrate the epidermis and interact with immune cells, triggering an inflammatory response and moisture to escape, making the skin dry and cracked.  

Eczema in infants should be optimally managed and may reduce the likelihood of sensitisation to a food through the skin [20]. Ensuring topical corticosteroids are used correctly and effectively along with moisturising at least twice a day is recommended [12]. Several resources have been developed to help parents manage their child’s eczema including how to do wet dressings and bleach baths where required.

Voukelatos S^1,2, Vale S^1,2,3, Joshi P^1,2, Said M^1,2

Maria Said is Chief Executive Officer of Allergy & Anaphylaxis Australia and Co-chair of the National Allergy Strategy.

Sally Voukelatos is a Health Educator with Allergy & Anaphylaxis Australia and is a member of the National Allergy Strategy Steering Committee.

Sandra Vale is Manager of the National Allergy Strategy and is affiliated with the University of Western Australia.

Dr Preeti Joshi is a paediatric clinical immunology/allergy specialist and is a staff specialist at the Department of Allergy and Immunology at The Children’s Hospital, Westmead. Dr. Joshi is Co-chair of the National Allergy Strategy.

Affiliations:

1. Allergy & Anaphylaxis Australia, Sydney, New South Wales

2. National Allergy Strategy, Sydney, New South Wales

3. The University of Western Australia, Perth, Western Australia

Further information:

https://preventallergies.org.au/https://preventallergies.org.au/healthcare-professionals/

https://preventallergies.org.au/healthcare-professionals/health-professionals-education-video/

ASCIA Food allergy prevention e-training for health professionals https://etraininghp.ascia.org.au/mod/page/view.php?id=134

ASCIA Paediatric atopic dermatitis (eczema) e-training for health professionalshttps://etraininghp.ascia.org.au/mod/page/view.php?id=135

For information and resources for health professionals and parents:

https://preventallergies.org.au/

https://nationalallergystrategy.org.au

https://allergyfacts.org.au

Health professionals can order bookmarks from Allergy & Anaphylaxis Australia free of charge –

https://allergyfacts.org.au/shop/nasr

References

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18. Australasian Society of Clinical Immunology and Allergy (ASCIA). ASCIA guidelines: Acute management of anaphylaxis. 2020.  https://allergy.org.au/hp/papers/acute-management-of-anaphylaxis-guidelines Last access 14 February 2020.
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