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Food Allergy Learning Zone
Declaration of sponsorship Novartis Pharma AG

Food allergy overview

Declaration of sponsorship Novartis Pharma AG
Read time: 50 mins
Last updated:4th Aug 2021
Published:4th Aug 2021

Food allergies are common and burdensome conditions, that are increasingly becoming more prevalent. Explore:

  • The prevalence of food allergies in our infographic
  • Different types of food allergy, their symptoms, and risk factors
  • Our interviews on the burden of food allergies, from misdiagnosis to social impact

Food allergy epidemiology

In the last several decades, the increasing prevalence of food allergy has become a significant public health concern for families and healthcare professionals around the world1. While the burden of food allergy is variable, it impacts people of all ages, ethnicities, and socioeconomic status1.

Global prevalence of food allergies

Current estimates of food allergy prevalence vary due to differences in age, geographic location, study methodologies, and awareness of food allergies1,2. However, food allergies are widely considered to be common and are continually increasing in prevalence2.

International population-based estimates of paediatric food allergy prevalence (Figure 1) can provide valuable insights into the disease burden1.

T1 Food Allergy_Fig1.png

Figure 1. Population-based estimates of current paediatric food allergy prevalence in various countries around the world (Adapted1).

In Europe, it is estimated that approximately 11–26 million people have food allergies3. If this were projected onto the global population, it would translate into an approximate global prevalence of 240–550 million food-allergic people3. A particular concern is also the incidence of food allergy in young children, which is estimated to be greater in toddlers (5–8%) than adults (1–2%)3.

The United States shows similar rates of food allergies. In a population-based cross-sectional prevalence study of over 50,000 households, 10% of the US population was shown to be affected by at least one immunoglobulin E (IgE)-mediated food allergy4.

However, cross-sectional prevalence surveys may overestimate food allergy prevalence5. Epidemiological studies that provide clinical confirmation through oral food challenges are more accurate, although these can be expensive and logistically challenging. Moreover, while such studies exist, they can lack consistent or standardised criteria for defining outcomes6.

Why is the natural history of food allergy important?

Not all allergies are the same in terms of their likelihood to resolve. Food allergies can differ in being either persistent or transient with the loss of the same food allergy over time.


Join Professor Alexandra Santos and find out why it is essential to understand the differences in natural history and how this can impact the management of food allergies in children.

Are there racial differences in food allergy burden?

Racial and socioeconomic disparities have been observed in the prevalence of food allergies1. An understanding of the aetiology of these disparities may help identify ways to reduce the inequalities and potentially eliminate them.

In a US population-based cross-sectional prevalence survey, significant differences in food allergy prevalence were observed in ethnic groups: Asian (11.4%), Black (11.2%), Hispanic (11.6%) and other non-White people (15.9%) all had a higher prevalence than White non-Hispanic (10.1%) people (P<0.001)4.

Infants of Black race (predominantly UK Afro-Caribbean or African) are associated with a higher risk of peanut-specific IgE sensitisation than White infants7

The Learning Early About Peanut Allergy (LEAP) screening study, a large randomised controlled trial in the United Kingdom, highlighted racial differences in the prevalence of food allergy. With the original aim to characterise the population and screen for the risk of peanut allergy, the LEAP screen study showed that infants of Black race (predominantly UK Afro-Caribbean or African) were associated with a significantly higher risk of peanut-specific IgE sensitisation than White infants (OR, 5.30 [95% CI, 2.85–9.86])7.

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Types of food allergy

Food allergies are a pathological and potentially fatal adverse immune response to a normally innocuous antigen present in food12.

How are food allergies defined?

Guidelines broadly divide adverse reactions to food into immune mediated and non-immune mediated (Figure 2). Immune mediated adverse reactions are further subdivided into IgE-mediated, non-IgE-mediated, or mixed IgE- and non-IgE-mediated13,14.

T1 Food Allergy_Fig2.png

Figure 2. Classification of adverse food reactions: Immune-mediated and non-immune-mediated mechanisms (Adapted13).

When consuming foods, antigens present on food normally induce an antigen-specific immune unresponsiveness known as oral tolerance15. Food allergies occur when oral tolerance to one or more dietary antigens does not develop15. Adverse reactions to foods or food components that do not utilise known immunologic mechanisms are considered food intolerances13.

What are the most common food allergens?

In IgE-mediated food allergies, exposure to a specific antigen in a trigger food will induce immediate and reproducible effects in the gastrointestinal tract, skin and/or respiratory system16. This requires prior food allergen sensitisation, and the development of a serum-specific IgE antibody to the food allergen.

While any protein can theoretically cause this sensitisation, according to the United States Food and Drug Administration (USFDA), 90% of allergic reactions are attributable to nine major food groups17:

  • Milk
  • Eggs
  • Fish
  • Crustacean shellfish
  • Tree nuts
  • Peanuts
  • Wheat
  • Soybeans
  • Sesame (to be included in 2023)

However, the most common food allergens differ around the world, possibly due to varying cultural dietary practices18. For example, peanut allergy is very uncommon in Asia (excluding Japan)19 while a predominate allergy in the United Kingdom, United States, and Australia, particularly in children less than 5 years of age5.

In Thailand, Japan, and Korea, wheat, egg, and milk are becoming the most common food allergens in childhood20. In other parts of Asia, shellfish is a leading cause of food allergy in adolescents and adults21.

Differences in prevalence across the globe may be attributed to variances in cultural dietary habits, such as early food introduction, as well as differences in food processing, skin care, and other cultural practices21,22. More research is ongoing to understand the factors that are critical in the development of food allergy22.

What are the symptoms of food allergy?

Following exposure to a trigger food, the symptoms of food allergy normally begin within minutes. This triggering of symptoms most often occurs within two hours of exposure in an an IgE-mediated response16. However, the timing of this reaction may be influenced by various co-factors, including alcohol consumption, physical exercise, and the specific medications23.

α-gal syndrome is also an exception. The sensitisation associated with this condition is initially triggered through tick bites, such as the lone star tick. Reactions can then occur within 2–6 hours after eating meat of mammalian origin24.

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Food allergy risk factors

The pathophysiology of food allergy is likely the result of genetic susceptibility, and an interaction of prenatal and postnatal environmental factors25. Lifestyle, culture, and behavioural factors, as well as diet and other exposures, may also impact the frequency, severity, and type of allergic reactions26.

Get to know the risk factors in food allergy with Professor Sharon Chinthrajah below, such as the delayed delivery of life saving medication and other allergic conditions.

How do genetics affect food allergy?

Two notable twin studies examined heritability in families and have shown a genetic component to food allergy27,28.

The first study of 14 monozygotic and 44 dizygotic twins demonstrated a significantly higher concordance for peanut allergy among monozygotic (64.3%) twins compared to dizygotic (6.8%) twins (P<0.0001)27. The overall heritability of peanut allergy was found to be 81.6% (95% CI; 41.6–99.7%) in a study where food allergy was assessed with a clinical history and a positive skin prick test (SPT) and/or peanut-specific IgE27.

Extensive studies have identified an association between a heterogeneous and complex set of genetic mechanisms and the development of food allergy25

A further study with 472 monozygotic and 354 dizygotic twins examined the rates of sensitisation28. Concordance rates for sensitisation were similarly shown to be much higher in monozygotic (52.1%) than in dizygotic twins (39.2%), with concordance rates higher among monozygotic twins sensitised to peanut (53% vs. 29%, P=0.002) and shellfish (58% vs. 45%, P=0.08) than dizygotic twins28. Estimated heritability to allergen sensitization ranged from 51% (95% CI, 0.34–0.66) to 68% (95% CI, 0.58–0.76)28.

However, there was discordance in the data between numerous twin pairs, suggesting that environmental factors, in addition to genetics, play a significant role in the development of food allergy28.

How does the environment in early life impact the risk of food allergy?

Mothers not only provide 50% of their genes to their baby, but they also provide a specific environment in which the baby lives for the first nine months. Following birth, mothers continue to have a major influence on the environment of the baby, especially while breastfeeding29.

Research has shown that early food introduction of potentially allergenic foods may decrease the risk of developing food allergies, and that protein transfer via breast milk is an important method of initial exposure to food30

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Burden of food allergy

A major consideration of food allergies is the impact on health-related quality of life for patients and their carers. Food allergy is associated with symptoms that only occur during an allergic reaction. These symptoms require patients to be continuously alert when eating to prevent potentially severe, or potentially fatal, allergic reactions. The mental health impact of living with food allergy can lead to depression, anxiety, post-traumatic stress, and bullying34.

Explore the burden of food allergy with Professor Alexandra Santos below and find out the significant day-to-day impact food allergy can have on patient lives.

How does food allergy impact children and adolescents?

In a study of 150 children (0–12 years) and 24 teenagers (13–17 years), food allergies were found to have a greater impact in adolescents than younger children in terms of emotional, dietary, and social quality of life35.

Specifically, the median Food Allergy Quality of Life Questionnaire (FAQLQ) score was shown to be significantly higher in adolescents compared with children (4.7 vs 3.5, P=0.007), highlighting a lower quality of life (Figure 1)35.

T1 Food Allergy_Fig3.png

Figure 3. Food Allergy Quality of Life Questionnaire (FAQLQ), Emotional Impact (EI), Food Anxiety, and Social and Dietary Limitations (SDL) scores from childhood to adolescence (Adapted35).

Adolescents also had a higher median social and dietary limitations (SDL) score (5.2 vs 4.0, P=0.002) and median emotional impact (EI) score (3.8 vs 3.1, P=0.02) than children. Food anxieties in children were also seen to be rising, with a median Food Allergy Quality of Life Questionnaire (FAQLQ) score increase of 0.18 points (95% CI, 0.12–0.26) per year35.

The study also found that the impact on family activities due to food allergy also lowers the quality of life and well-being of all family members35.

However, studies have found that oral immunotherapy (OIT) and the oral food challenge (OFC) are associated with improvements in health-related quality of life36. In a meta-analysis of 13 publications, a mean change of –1.25 (P<0.001) and –0.78 (P=0.052) was observed in health-related quality of life scores following OIT and OFC, respectively36.

Moreover, five OIT studies demonstrated significant health-related quality of life improvements with OIT compared to placebo, with an overall standardized mean difference of –0.56 (P=0.007)36.

Bullying and food anxiety

Food anxieties and bullying can have a large impact on the quality of life of children and adults living with food allergies.

Bullying

In a survey of 353 food-allergic children and adults, 24% stated they were harassed because of their food allergy37. The most common site of bullying was at school, with 82.4% facing bullying, teasing, or harassment from classmates. Moreover, 21.4% of students reported that teachers and school staff were also perpetrators of bullying37.

In a study of school teachers, only 4% (N=203) claimed to have personally witnessed or known about bullying towards food-allergic school children, and 99% underestimated the frequency of bullying directed against food-allergic students38.

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References

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  37. Lieberman JA, Weiss C, Furlong TJ, Sicherer M, Sicherer SH. Bullying among pediatric patients with food allergy. Ann Allergy, Asthma Immunol. 2010;105(4):282–286.
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