Childhood food allergy and intolerance

Symptoms and signs of food allergy, when to consider excluding foods from a child's diet and the latest advances in food allergy research.

Food allergy and intolerance is an area of medicine that can be both confusing and controversial, with new research emerging regularly. It can be very difficult to distinguish between different types of adverse reactions to food, so rates of self-reported food allergy are higher than proven food allergy using objective methods.

The EU has identified 14 major allergens and by law, these must be declared on food labels. They are cow’s milk, hen’s egg, fish, shellfish, cereals containing gluten, soya, peanut, tree nuts, sesame, celery, mustard, crustaceans, molluscs and sulphites.

Although excluding an uncommon or infrequently consumed food from the diet, such as prawns, may have no particular nutritional significance, attempting to exclude a whole food group, such as milk, is more likely to be problematic, especially in young children and infants.

The first step in ensuring satisfactory diagnosis and management of food allergy and intolerance is to have a good understanding of the difference between the two terms.

Food allergy is an adverse reaction to a food protein, which is caused by a specific immune mechanism. It can be subdivided into two types. IgE mediated food allergy is antibody mediated and typically leads to immediate symptoms within minutes of being exposed to the food. Non-IgE mediated food allergy typically causes more delayed symptoms two to 48 hours after consumption.

In contrast, food intolerance is an adverse reaction to a food, caused by a mechanism that does not involve the immune system, such as lactose intolerance.


According to NICE guidelines,1 symptoms of food allergy may be immediate, delayed or both, and can occur in the skin, GI and respiratory systems (see table 1). Symptoms may develop after a very small trace of the food has been ingested, or in the case of some severe allergies, such as peanut, through airborne exposure. Symptoms of food allergy can be life-threatening, specifically in the case of anaphylaxis.

Table 1. Signs and symptoms of possible food allergy according to NICE guidelines1

IgE mediated (immediate)

Non-IgE mediated (delayed)

The skin

  • Pruritus
  • Erythema
  • Acute urticaria
  • Acute angioedema (most commonly in the lips and face, and around the eyes)

  • Pruritus
  • Erythema
  • Atopic eczema

The GI system

  • Angioedema of the lips, tongue and palate
  • Oral pruritus
  • Nausea
  • Colicky abdominal pain
  • Vomiting
  • Diarrhoea
  • Gastro-oesophageal reflux disease
  • Loose or frequent stools
  • Blood and/or mucus in stools
  • Abdominal pain
  • Infantile colic
  • Food refusal or aversion
  • Constipation
  • Perianal redness
  • Pallor and tiredness
  • Faltering growth, plus one or more GI symptoms above (with or without significant atopic eczema)

The respiratory system (usually in combination with one or more of the above symptoms and signs)

  • Upper respiratory tract symptoms – nasal itching, sneezing, rhinorrhoea or congestion (with or without conjunctivitis)

  • Lower respiratory tract symptoms - cough, chest tightness, wheezing or shortness of breath)


  • Signs or symptoms of anaphylaxis or other systemic allergic reactions


The cornerstone of the diagnosis of food allergy is to take an allergy-focused history.1 A detailed and comprehensive history will inform the clinician as to whether diagnostic tests should be undertaken. A skin prick test and/or a specific IgE (blood) test are recommended for the diagnosis of IgE mediated food allergy, but these should only be performed by those with the competencies to interpret the tests.

Use of a blood test may be more accessible than skin prick testing in primary care, however it is only recommended to test for foods that are implicated in the clinical history.

A positive skin prick test or specific IgE test merely indicates the presence of antibodies (sensitisation) and does not confirm clinical allergy. However, a positive test coupled with a clear history of a reaction may confirm a diagnosis, although an oral food challenge in a hospital setting may be required for confirmation.

There are no validated tests for the diagnosis of non-IgE mediated food allergy, apart from avoidance of the suspected allergen for about four weeks, followed by reintroduction or a home food challenge to confirm the diagnosis. In the case of suspected cow’s milk allergy in an infant, a maternal exclusion diet (if the child is breastfed) and/or a hydrolysed or amino acid formula may be required.2

In the UK, the most prevalent food allergies in early childhood are milk and/or egg. Recent UK data suggest 1-3% of children in the UK have a milk allergy and approximately half will outgrow it by the age of one year.3,4 Allergies to peanuts and tree nuts tend to occur in later childhood, with a resolution of approximately 20%.

Food allergens can sometimes cross-react with each other (for example, pecan and walnut), or with some plant allergens (for example, pollen food syndrome) or be exacerbated by exercise (for example, wheat allergy).

Dietary management

Management of food allergy and intolerance involves individualised dietary exclusion of the offending allergen. Some children may be able to tolerate traces of the food or its cooked form (for example, baked egg but not raw egg). However, some may require total exclusion.

Care must be taken to ensure the diet remains nutritionally adequate and optimal growth is maintained, particularly in the case of suspected multiple food allergies. In children under two years of age, extensively hydrolysed formulas are suitable for mild-moderate cases of cow's milk allergy.2 An amino acid based formula can be used for severe cases of cow's milk allergy or multiple food allergy.2 

Suboptimal intake of nutrients has been reported, particularly protein, calcium, vitamin D and zinc, but nutritional deficiencies can occur even when nutritional supplements are consumed.5 Practical advice on the level of avoidance required, alternative foods, cross-contamination, food label reading and nutritional supplements can be provided by a dietitian.

Signs of development of tolerance and food challenge/reintroduction plans should be discussed with an appropriately trained doctor or dietitian. In the case of mild to moderate non-IgE milk allergy, reintroduction can take place at home using a staged reintroduction plan, known as the milk ladder.2

Recent advances in food allergy research

Although the current management of food allergy is dietary avoidance, with education and provision of emergency medication where appropriate, a number of oral immunotherapy research studies are being undertaken internationally.

Peanut oral immunotherapy involves the administration of small but increasing doses of peanut protein in a supervised clinical setting to children who are allergic to peanut. A UK-based phase II, randomised, controlled, crossover trial of peanut oral immunotherapy demonstrated that children who successfully completed the protocol had a 25-fold increase in their peanut threshold, and their caregivers had a significant improvement in quality of life.6

Larger studies are needed to improve the safety and efficacy of this form of treatment and it is not recommended in clinical practice at present, but it offers promise for the future.

Another UK-based study, the Learning Early About Peanut Allergy (LEAP) study, demonstrated a successful 11-25% absolute reduction in the risk of peanut allergy in high-risk infants if peanut was introduced between four and 11 months of age.7

European Academy of Allergy and Clinical Immunology guidelines regarding the early introduction of complementary foods have indicated that the introduction of highly allergenic foods, such as peanut, need not be delayed past four or six months of life.

However, they do not actively recommend the introduction of peanut between four and six months of age in high-risk infants. Interim guidelines on weaning children at high risk of peanut allergy have been published in response to the LEAP study.8

  • Dr Kate Maslin is senior research fellow , School of Health Sciences and Social Work, University of Portsmouth

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  1. NICE. Food allergy in under 19s: assessment and diagnosis CG116. London, NICE, February 2011
  2. Venter C, Brown T, Shah N et al. Diagnosis and management of non-IgE-mediated cow’s milk allergy in infancy – a UK primary care practical guide Clin Transl Allergy 2013; 3(1): 23
  3. Schoemaker AA, Sprikkelman AB, Grimshaw KE et al. Incidence and natural history of challenge-proven cow’s milk allergy in European children – EuroPrevall birth cohort Allergy 2015; 70: 963-72
  4. Venter C, Pereira B, Voigt K et al. Prevalence and cumulative incidence of food hypersensitivity in the first three years of life. Allergy 2008; 63(7): 354-9
  5. Meyer R, De Koker C, Dziubak R et al. A practical approach to vitamin and mineral supplementation in food allergic children Clin Transl Allergy 2015; 5: 11
  6. Anagnostou K, Islam S, King Y et al. Assessing the efficacy of oral immunotherapy for the desensitisation of peanut allergy in children (STOP II): a phase 2 randomised controlled trial Lancet 2014; 383: 1297-1304
  7. Du Toit G, Roberts G, Sayre PH et al. Randomized trial of peanut consumption in infants at risk for peanut allergyN Engl J Med 2015; 372(9): 803-13
  8. Fleischer DM, Sicherer S, Greenhawt M et al. Consensus communication on early peanut introduction and the prevention of peanut allergy in high-risk infants World Allergy Organ J 2015; 8(1): 27

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