Allergy FAQs with The Allergy Dietitian, Dr Penny Barnard

walnut, childrens meal. nut roast. allergens in childrens diet


Question 1: How common is it to have a baby with an allergy?


Answer: Food allergies changes with age; the type of allergies seen in adults differ to children and these differ to allergies in babies. In the UK, 5% of babies will develop an allergy in the first 2 years of life. Approximately half of these will be IgE-mediated reactions and the other half non-IgE.


Question 2: What is the difference between an IgE reaction and a non-IgE reaction?



An allergic response to food involves the immune system. An IgE-mediated allergic reaction usually occurs within two hours of eating the food and involves IgE antibodies. Symptoms include an itchy rash, swelling of the eyes, face and lips and sometimes vomiting and diarrhoea. This reaction can involve symptoms of the airways such as coughing and wheezing, difficulty in breathing & anaphylaxis. This type of allergic reaction is most commonly caused by egg, milk & peanut in children under 2 years of age. A non IgE-mediated food allergy has a more delayed reaction time, usually happening two hours after exposure to the allergen. Sometimes symptoms will show up after 2-3 days. Common symptoms include diarrhoea, vomiting, constipation, abdominal cramps and an eczema flare up. This type of reaction doesn’t normally involve the production of IgE antibodies against a particular food, but a different type of immune reaction involving other cells of the immune system.


Question 3: So, of the five percent of babies under two with an allergy, how many of these will have a severe allergy as opposed to a minor one?


Answer: Roughly half will have an IgE reaction and the other half will have a non IgE. The most common IgE allergy under two is to egg. Reactions may also occur to peanuts, tree nuts, sesame and fish. Severe allergic reactions in babies are rare. The most common non-IgE allergy is to milk.


Question 4:Are allergens increasing or is our understanding of allergies improving with testing and diagnosing?


Answer: It is a mixture of both components. A lot more is known about allergies and diagnostics have got a lot better. There are different foods in people’s diets now than there were compared to 30/40/50 years ago. With the movement of people comes the movement of food. As different foods come into the country, they become a more regular part of the diet.


Question 5: Why does the NHS recommend introducing allergens from six months?


Answer: In the UK guidance around the introduction of allergens have come from two major studies. Recommendations are on the early introduction of egg and peanut. The main study, known as The Leap Study, involved high risk children with an existing egg allergy and moderate to severe eczema. They looked at whether the children had an existing peanut allergy or whether they went on to develop a peanut allergy, depending on whether they had peanut in their diet or not. The babies who took part in this study are now teenagers and they are still followed up. Due to the results of the study, babies are now advised to introduce peanuts into the weaning diet from 4-6 months.

A smaller study was carried out on breastfeeding babies in London and the surrounding areas, which looked at early allergen introduction. Allergens were introduced at three months of age and the development of allergies was studied in this group of babies. Six allergens were introduced. Both studies have shown the importance of introducing allergens early in the weaning diet and maintaining them in the diet to try and prevent children from developing food allergies. It is also very important to have a varied diet, to not stick to just a handful of foods, but to explore tastes, smells and textures.


Question 6: By early on in the diet, do we mean around six months?


Answer: For the majority of the population it is recommended to start introducing allergens from 6 months of age. High-risk groups of babies are advised to start adding them to the weaning diet from 4-6months of age.


Question 7: How would a parent know if their child is at high-risk of having a food allergy?


Answer: There are 2 main factors that would put a baby in the high-risk category for developing a food allergy. Firstly having early onset, moderate to severe eczema. This would be eczema appearing from around three to four months of age or earlier and requiring treatment. Secondly a child with a pre-existing immediate food allergy.

There is also evidence in breastfed babies to suggest if cow’s milk formula is given in the first week of life only to supplement breast milk there is an increased chance of baby developing a milk allergy when dairy is later introduced.

 You should seek medical advice if your child is in a high-risk category to discuss early introduction of allergens into the weaning diet. It may be necessary to have allergy testing before egg and peanut is introduced.


Question 8:  For those children who are not high risk and do not have a pre-existing allergy, what are some practical tips for introducing allergens from six months?


Answer:Weaning should commence using whatever technique the parents are happy and comfortable with, for example starting off with bitter vegetables, fruit or baby rice etc. The majority of parents nowadays go down the vegetable-based weaning route. Once initial tastes are taken for a few weeks, the first suggested allergen to introduce is egg. It should be a hard-boiled egg which is pureed or mashed down and then added to one of their favourite vegetables as a meal. Start off with ¼ teaspoon of mashed egg added to a favourite vegetable. It is recommended to wait three days, then up the portion of egg to ½ teaspoon. Wait another three days and up to 1 teaspoon then again to a heaped teaspoon. If that is tolerated well, the egg can be offered however you wish to serve to. Cooking eggs at a lower temperature or for less time makes them more allergenic, for example offering egg with a runny yolk is more likely to cause an allergic reaction. Also scrambled egg can be more allergenic as they are only cooked for a minute or two and the consistency can vary throughout.

The second allergen to introduce would be peanuts. The same process as with the egg can be carried out increasing the amount every few days, starting with a ¼ teaspoon leading up to a heaped teaspoon. Smooth peanut butter without sugar or salt can be used and could be mixed into vegetables or porridge. Finely ground unsalted peanuts could also be used if preferred.


Question 9: Is it recommend to trial the allergen on the skin before feeding it to your baby?


Answer: No, that is not recommended.  Children can become sensitised through the skin and ideally we want exposure to be through the mouth.


Question 10: Once an allergen has been safely introduced into the diet, why is it important to maintain the allergen?


Answer: It is so important once introduced to maintain the allergen in the diet. If there are long periods of time when the allergen is not offered we can become allergic to it. Try and offer allergens in the diet once a week.


Question 11: Is it important to have all 14 allergens every week?


Answer: The evidence there is on allergy prevention is regarding egg and peanut, so they are the most important allergens to keep offering in the diet. A tip for tree nuts is to, once you know the baby has tolerated them individually, to grind them together and use them in cooking or sprinkle over porridge, yoghurt etc. It is important to consider that shop-bought ready-made baby foods rarely contain allergens. As a result the baby is not being exposed to any allergens which could potentially increase the risk of developing a food later in life.


Question 12:‘My son had a contact allergy to aubergines, is it okay to keep offering it to him?’


Answer: This has become more common in the last eighteen months. More babies are being introduced to aubergine as a bitter vegetable and it is popular in current weaning books. Vegetables that can potentially cause irritation to the skin are those that are acidic and/or contain histamine. When a child is having an allergic reaction, the cells release histamine which cause the symptoms of an allergic reaction. Foods with histamine in them can cause a similar reaction e.g. redness. Aside from aubergine, foods such as tomatoes, strawberries, and citrus fruits can also cause contact reactions. So it is likely to be a contact reaction rather than an allergic reaction. You can therefore continue to offer the food and a barrier cream can be applied around the mouth before the meal.


Question 13: So, should you then avoid that food or is it ok to continue giving it to your baby?


Answer: No, you don’t need to avoid that food as it is not likely to be a serious reaction and your baby shouldn’t be disturbed by it. There’s no need to avoid the food again. You might like to take a break from that food for a few days or weeks but you don’t need to avoid it forever.  However, if it caused a sore or itchy area you might want to avoid it if your child is in discomfort.  This irritation can sometimes occur less with cooked food, for example, there can be more of a reaction with raw tomato compared to cooked tomato.


Question 14: Is it possible to grow out of an allergy?


Answer: Yes, lots of people grow out of food allergies. It is common for children to grow out of non IgE mediated allergies such as milk allergy. Children are less likely to grow out of a peanut, tree nut and sesame allergy, but a small number will.