Food allergies are extremely common, and affects about 6-8% of all children.
Food allergy is most common in infants and toddlers, with 1 in 40 infants suffering from cow’s milk allergy. Also common are allergies to egg, nuts, soya, wheat and fish/shellfish .
There are various types of food allergies.
Different Types of Food Allergies
1. Immediate food allergies
Immediate food allergies are driven by the IgE antibody which leads to release of histamine and other substances from allergy cells in the body. These may result in:
- Hives and/or urticaria (nettle rash)
- Angioedema (swelling)
- Vomiting or diarrhea
- In more severe allergic reactions (anaphylaxis) may result in difficulty breathing due to swelling inside the throat or wheezing or becoming drowsy and listless.
Immediate allergic reaction usually occurs within 20 minute of being exposed to the culprit food but can occur up to 2 hours after exposure.
2. Pollen-food syndrome / Oral allergy syndrome
This is a milder form of immediate food allergy which usually occurs in later childhood in children who are allergic to tree and grass pollens. Due to cross-reactivity between the proteins found in pollens and raw fruits and vegetables these children can develop local allergic symptoms in the mouth and throat which do not usually lead to anaphylaxis.
Importantly, when fruits and vegetables are thoroughly cooked or processed they no longer cause oral allergy syndrome as the cross-reactive proteins are destroyed.
3. Delayed Food Allergies
There are also delayed allergies which can result in eczema flares or problems in the gut such as colic, reflux, pain, loose mucousy and /or bloody stools and constipation. These delayed allergic reactions usually occur at least 2 hours after eating the food and may occur the following day(s) which makes diagnosis and management of this type of food allergy more difficult. This article will discuss the management of immediate food allergy.
Management of food allergy
Management of food allergy is based on educating patients and their families on strict avoidance of the culprit food and prompt treatment of allergic reactions, resulting from accidental exposure.
Dietetic advice as part of a multidisciplinary consultation has been shown to improve allergen avoidance with a resulting reduction in accidental allergen exposures in the community. Dietetic advice is also important in terms of ensuring adequate nutrition in children with food allergies and finding alternative foods for the child to eat.
Children and families are provided with a written personalised emergency management plan on how to recognize and treat allergic reactions. This plan should be shared with the child’s nursery or school and other persons who have responsibility for looking after the child.
The child’s emergency plan may include antihistamines alone. If the child has had previous anaphylaxis or has food allergy and asthma requiring regular medication they will also require the provision of adrenaline auto injector devices and training on how to use these. As peanut and tree-nut allergies can be unpredictable, many children with peanut and tree-nut allergy are prescribed adrenaline auto injectors even if they have not had previous anaphylaxis and they do not have asthma.
Recent advances in allergy research have resulted in a more active approach to managing food allergy. These approaches include food allergy prevention by early dietary introduction of potentially allergenic foods, and inducing tolerance to known foods allergens.
Food allergy prevention
Previously, the Department of Health recommended delaying the introduction of peanut until 3 years of age if there was a history of allergy in the family. This recommendation was based on limited data and has now been withdrawn.
Currently, Department of Health guidelines recommend exclusive breast-feeding until 6 months, complimentary feeding ‘at around’ 6 months and avoidance of potentially allergenic foods (peanuts, tree-nuts, seeds, milk, eggs, wheat, fish or shellfish) until after 6 months of age. However, European and American infant guidelines recommend introducing complimentary foods from 4 to 6 months of age.
There are several studies which have shown an association between earlier consumption of cow’s milk, egg and peanut and a reduction in allergies to these foods in childhood; these studies, however, do not demonstrate causation.
Results from two large interventional studies are now available, which can provide further clarity:
The LEAP study includes 640 children who had severe eczema or egg allergy at age 4-11 months thus had an increased chance of developing peanut allergy. Each child was randomly assigned to either eat peanut-containing foods 3 times a week or avoid peanut to see which approach would best prevent peanut allergy. At age 5 each child was fed peanut to see whether they were allergic to peanut or not.
The EAT Study is a study of 1303 children who were exclusively breastfed at 3 months of age. Each child was randomly assigned to introduce six allergenic foods (cow’s milk, egg, wheat, sesame, fish and peanut) into the diet from 3 months of age, alongside continued breastfeeding or avoiding these foods until they were 6 months old. At age 3 years each child is being assessed to see whether they are allergic to any of these foods.
Treating established foods allergies
Certain food allergies, such as cow’s milk, soya, egg and wheat, are usually outgrown after a few years of avoiding the food; however, fish, shellfish, peanut and tree nut allergy are not usually outgrown.
Food desensitisation (giving a child with a certain food allergy gradual increasing amounts of that food under close hospital supervision) for peanut, cow’s milk and egg shows considerable promise as a future form of active treatment but is not yet ready for routine clinical care. Importantly, food desensitisation does not cure food allergies as studies have shown that if the child stops eating the food for a few weeks the allergy returns in many cases. Desensitisation should not be tried outside hospital supervision as severe allergic reactions have been reported whilst undergoing this.
Recent studies have shown that 70-75% of cow’s milk and egg allergic children can tolerate cow’s milk and egg respectively when it is extensively heated. This is because heating cow’s milk and egg denatures the allergenic proteins in these foods and thus allows some children to tolerate them.( When possible, this not only improves the child’s diet and quality of life but has also been shown to accelerate the resolution of unheated cow’s milk and egg.
In two studies, children who incorporated baked milk into their diet were 16 times more likely to become tolerant to all forms of cow’s milk than children who avoided cow’s milk; similarly children who incorporated baked egg products into their diet were 14 times more likely to become tolerant to regular egg, compared with children avoiding all forms of egg.( Children regularly eating baked egg products also tolerated regular egg on average 2-2.5 years earlier. It is difficult to know which children can tolerate baked forms of cow’s milk and egg, as some children can have severe allergic reactions, even to baked forms of cow’s milk and egg. Thus this should only be considered after assessment by an allergy specialist, and should not be tried at home before assessment.
Research into food allergy prevention and tolerance induction has gained momentum in recent years. A more active approach to food allergy prevention and management is likely to result from this research in allergy centres around the world which will have many advantages for food allergic children and their families.