NHD Paediatric Hub

The introduction of allergens during weaning

Aliya heads up our Paediatric Hub this month. Here she focuses on the introduction of allergens during weaning, including the current guidelines and the growing evidence around how food allergies develop.

Twitter : @aliyaporter
Facebook: @porter_nutrition

Aliya Porter, RNutr

Freelance Registered Nutritionist

Food allergy affects 3-6% of children in the developed world(1) and 5-8% of toddlers.(2) The prevalence of Cow’s Milk Allergy (CMA) in children living in the developed world is approximately 2% to 3%, making it the most common cause of food allergy in the paediatric population. Only among breastfed infants is the prevalence lower (0.5 %).(3)

Food allergies can impact a child’s physical, emotional and mental health, as well as in rare cases cause loss of life, so the reduction of food allergies as well as the safe introduction of allergens during weaning is paramount in paediatrics.

For the purpose of this article, weaning is defined as the introduction of solids, rather than stopping breast or formula milk. This definition of weaning (the introduction of solid foods) is how it is commonly understood by parents.


UK guidelines state that babies should commence the introduction of solids around six months but not before four months. They should commence when babies can sit up and hold their heads steady, pick things up and put them in the mouth, and then they can actually swallow – they have lost their tongue thrust reflex which would mean more food went around the mouth than went into it and got swallowed.(4) The guidelines also say that allergens should be introduced with the commencing of solids at six months.(5)

This advice represents a change from previous guidance. In 1998/1999 COT recommended avoiding peanuts during pregnancy, breastfeeding and the infant diet until the child was three years of age. This advice changed in 2009 when they recommended no delay beyond six months for those with no existing allergies or eczema, and to seek medical advice for those who did.

BSACI guidelines

Alongside current guidance, there is also guidance from the British Society of Allergy and Clinical Immunology (BSACI) about the introduction of allergens alongside other solid foods.(6)

The BSACI guidelines state that children who don’t have eczema or a food allergy (even if their parents do) should introduce eggs and peanuts once baby starts solids (not as the first taste but at six months) and then other allergens between six and 12 months – not delaying the introduction.

For children who have eczema or a known food allergy, they are encouraged to introduce allergens (not any they are known to be allergic to already though) from four months, alongside other foods.

The reason those with eczema is highlighted alongside existing food allergies is because Approximately 40% of infants and young children with moderate to severe Atopic Eczema have food allergy.(7)

The EAT and LEAP studies
concluded that high-risk infants (those with eczema or existing food allergies) needed to introduce allergens – specifically peanut and egg – earlier than six months to see the same benefit in the reduction of risk of developing an allergy.(8) The LEAP and EAT studies emphasised the importance of not just introducing peanut and egg but also continuing with the consumption of these foods on a regular basis. The recommendation is to have the equivalent of one heaped teaspoon a week of peanut butter (mixed with water/breast milk or a vegetable to reduce choking risk) and one egg (mashed if introduced before six months and mixed with breast milk or water) per week until five years of age.(6)

Is it just the introduction of allergens and the inclusion of allergens that is important?

Research commissioned by the Food Standards Agency (FSA) followed up almost 1200 infants until the age of two. The research showed that breastfeeding whilst introducing solids (p=0.044), breast and formula feeding whilst introducing solids (p=0.008), diversity of diet (p=0.02) and following the infant feeding guidelines (p=0.027 all had a protective effect against the development of a food allergy.

Following the infant feeding guidelines meant higher fruit and fish consumption and lower crisp, commercial baby food and potato product consumption.(9)

The FSA research(9) confirms the need to encourage the introduction of a balanced, unprocessed diet alongside breastfeeding, where possible under the World Health Organisation recommendations to breastfeed until two years of age.(10)


More recently, the recommendation for children who do not have high risk to introduce allergens has been brought into question by a meta-analysis and systematic review carried out by researchers at Imperial College London. They found that a meta-analysis of nine trials (4811 participants) showed high-certainty evidence that early introduction of egg (between three and six months of age) was associated with a decreased risk of egg allergy. Their further meta-analysis of four trials (3796 participants) showed high-certainty evidence that introducing peanut between three and 10 months of age was associated with a decreased risk of peanut allergy. They also showed very low certainty evidence for the early introduction of cow’s milk and other allergens in reducing allergies. They did recognise, however, that there are challenges in the delivery of allergens to babies before six months in order to offer them early.(11)

More research is needed to establish whether guidelines need to be updated.

There is growing evidence around the role of the skin in the development of food allergies. It is early days but there are signs that if food comes through the skin first this can lead to food allergies.(12) This would explain the link between eczema and food allergy risk, because the skin barrier is weakened in eczema. As research develops it may lead to a change in the recommendations around the mechanism for offering allergens – spoon feeding rather than baby-led weaning where children pick up the food.



Introducing allergens early in the weaning process is important. The definition of early depends on whether the child has eczema or a known food allergy, or they don’t. The key thing is that introduction should not be delayed. Given the guidance was to wait to introduce peanuts until the age of three, many parents are still not sure about the latest advice – particularly those who rely on grandparents for information.

  • Learn the signs of an allergic reaction (see table below).
  • When they introduce solid foods, offer vegetables, fruit, starches and proteins, then once baby is taking these (don’t leave it longer than a few weeks), introduce egg and peanut, followed by other allergens.
  • Introduce allergens on their own rather than together, leaving at least a day between them.
  • Give a good amount of allergen at each sitting rather than a tiny amount – half a baby spoon rather than just the tip. The BSACI recommends egg over the course of a week and two teaspoons of smooth peanut butter over the course of a week.(1) The peanut butter needs to be mixed with fruit, veg, or rice to reduce the choking risk. Eggs should be Lion or Laid in Britain eggs if they are not served fully cooked. Peanuts should be offered ground or as nut butter, not whole or coarsely cut, until five years of age.
  • Having a wide variety of foods from the five main groups is important to help reduce the risk of developing an allergy, as well as for the child's general health.


Food allergy – common symptoms – usually straight after eating the food but can be delayed https://www.nhs.uk/conditions/food-allergy/

Anaphylaxis symptoms – usually develop suddenly and get worse quickly https://www.nhs.uk/conditions/anaphylaxis/ **

Feeling dizzy or lightheaded

Feeling lightheaded or faint

Itchy skin or a raised rash (hives)

Breathing difficulties – such as fast, shallow breathing

Swelling of the lips, face and eyes (angioedema)


Coughing, wheezing, breathlessness, noisy breathing, or a hoarse voice

A fast heartbeat

Sneezing or an itchy, runny or blocked nose

Clammy skin

Feeling sick or being sick

Confusion and anxiety

Tummy pain

Collapsing or losing consciousness

** There may also be other common allergy symptoms 



  1. Rona RJ, Keil T, Summers C, Gislason D, Zuidmeer L, Sodergren E, et al. The prevalence of food allergy: a meta-analysis. J Allergy Clin Immunol  2007;120:638-46.
  2. Pawankar R, et al, 2013 quoted by AllergyUK (2023) found at https://www.allergyuk.org/about-allergy/statistics-and-figures/ Accessed on 29th May 2023
  3. Lifschitz C, 2015 - quoted by AllergyUK (2023) found at https://www.allergyuk.org/about-allergy/statistics-and-figures/ Accessed on 29th May 2023
  4. NHS (2023) How to Start Weaning Your Baby found at: https://www.nhs.uk/start-for-life/baby/weaning/how-to-start-weaning-your-baby/ Accessed on 29th June 2023
  5. NHS (2021) Food Allergies in Babies and Young Children. Found at https://www.nhs.uk/conditions/baby/weaning-and-feeding/food-allergies-in-babies-and-young-children/ Accessed 29th May 2023
  6. BSACI (2018) Preventing Food Allergy In Your Baby: A Summary For Parents. Found at https://www.bsaci.org/wp-content/uploads/2020/02/pdf_Infant-feeding-and-allergy-prevention-PARENTS-FINAL-booklet.pdf. Accessed 29th May 2023
  7. AllergyUK (2023) Statistics and Figures. Accessed at https://www.allergyuk.org/about-allergy/statistics-and-figures/ on 29th May 2023
  8. Roberts G. et al (2022) Defining the window of opportunity and target populations to prevent peanut allergy. JACI – Food Allergy and Gastrointestinal Disease. Volume 151. Issue 3. P1329-1336 https://www.jacionline.org/article/S0091-6749(22)01656-6/fulltext
  9. Food Standards Agency  (2011) The prevalence of food allergy and weaning practices in a birth cohort of UK infants by Roberts et al. Accessed at https://www.food.gov.uk/sites/default/files/media/document/t07046report.pdf on 29th May 2023
  10. World Health Organisation (2021) Infant and Young Child Feeding. Accessed at https://www.who.int/news-room/fact-sheets/detail/infant-and-young-child-feeding on 29th May 2023
  11. Scarpone R, Kimkool P, Ierodiakonou D, et al. (2023) Timing of Allergenic Food Introduction and Risk of Immunoglobulin E–Mediated Food Allergy: A Systematic Review and Meta-analysis. JAMA Pediatr. 2023;177(5):489–497. https://jamanetwork.com/journals/jamapediatrics/fullarticle/2802512
  12. Conaway, B (2022) Allergies and Eczema: What’s the Link? Accessed at  https://www.webmd.com/skin-problems-and-treatments/eczema/eczema-allergies-link#:~:text=A%20lack%20of%20filaggrin%20dries,to%20get%20into%20the%20body on 29th May 2023