CONDITIONS & DISORDERS
Farihah Choudhury Health and Wellbeing Coordinator, University of Southampton Farihah is a Prospective Master’s student of Nutrition for Global Health. She is interested in public health nutrition, particularly in changing population health patterns as a result of dynamic food environments, food security and food waste, food poverty, food marketing and literacy.
REFERENCES Please visit the Subscriber zone at NHDmag.com
ADULT ONSET FOOD ALLERGIES Food allergy in adults is seeing a steady rise in developed countries. This article takes a look at the current understanding of food allergies and examines the reasons behind the increase in prevalence. In October 2018, NHD published a review of the current status of food allergy, in which we focused on paediatric food allergy.1a In several ways, paediatric food allergy is easier to fathom than that for adults. Many would hold late exposure to allergenic foods accountable, or poor diversification of infant diets1b,2,3 and would promote growth of beneficial gut microbiota to mitigate adverse health conditions later in life. Given this, the phrase ‘allergic reaction’ for most probably conjures up an image of a child with steadily swelling lips or irritated skin. After the recent inquest into the death of Natasha Ednan-Laperouse, the 15-yearold schoolgirl who had a fatal allergic reaction after eating a sandwich from Pret a Manger in 2016,4 an urgent reconsideration of food labelling on items sold in outlets was called to be had in the UK. However, although allergic reactions are more prevalent in children, and often more severe, adult onset food allergy is not uncommon and is seeing a steady rise in developed countries. Adult allergies present more of a conundrum, to the public and health practitioners alike: why would a food that has never caused any issue before, seemingly begin to incite an allergic reaction out of nowhere? THE ALLERGY DEBATE
The relatively sudden increase in allergy prevalence has not yet been 36
www.NHDmag.com April 2019 - Issue 143
pinned down to a single cause – many cite genetic predisposition (atopy) or epigenetic interactions with the environment.5-6 Some would argue the role of air pollution7 and others the globalisation of the food industry.8 Nearly 52% of Americans develop food allergies after the age of 18,9 and compared with infant-onset allergies, these are more likely to persist. This is in part due to the fact that allergic reactions in children are caused by poorly formed antigens that fail to respond to usually innocuous agents, whereas adult food allergies are caused by the loss of this previously well-developed defence mechanism. Adverse reactions to food can be separated into reactions which are intrinsic to the host (allergies, aversions and intolerances) and reactions intrinsic to the food (food poisoning). Immune-mediated hostintrinsic reactions, ie, food allergies, include immunoglobulin-E (IgE)mediated and non-IgE-mediated food allergy, cell-mediated food allergy, mixed reaction food allergy and coeliac disease. CURRENT UNDERSTANDING
Allergy research on the whole is a constantly developing area and much of the gaps in our understanding are yet to be filled. Much more is established about the immunology of IgE-mediated allergies than non-IgEmediated, though this is worrying, as
CONDITIONS & DISORDERS Table 1: Symptoms of food allergies IgE-mediated
Non-IgE-mediated
Gastrointestinal
Nausea, vomiting, abdominal pain and cramping, diarrhoea
Reflux, vomiting, diarrhoea, abdominal pain and distension, abnormal bowel biopsy
Dermatological
Acute rash
Rare: rash, dermatitis herpetiformis
Respiratory
Nose running and sneezing, eyes watering, swelling of lips, mouth and throat, can affect ears, wheezing/ Very rare: Heiner’s syndrome, recurrent bronchospasm, coughing, breathlessness, pneumonia inability to speak (symptoms rarely seen in isolation)
Cardiovascular
Hypotension, changes in heart rate, dizziness or faintness
Generalised
Anaphylaxis
the implication is that many people experience extreme allergic reactions and even anaphylaxis seemingly out of the blue (as non-IgE-mediated allergy symptoms have a later onset) and nobody will have assumed otherwise – neither medical professionals, nor the sufferers themselves. Recent fatalities are a testament to seemingly disproportionate allergic reactions to perceivably innocuous, or previously unproblematic, levels of exposure. Moreover, much less has been elucidated in terms of adult food allergies compared with paediatric allergy. HOW DO YOU KNOW YOU’RE ALLERGIC?
The enigmatic nature of allergy onset and diagnosis means that there has been speculation aplenty about what does or does not constitute an allergy and how best to avoid symptoms and reactions. Many err on the side of overcaution and believe they have allergies when they don’t. Others underestimate the risks and dismiss their symptoms. This understandably occurs especially amongst adults who have not previously had a food allergy. A European meta-analysis of studies conducted between 1990-2007 determined that self-reported allergy is thought to be anywhere between 3-35%10 in the UK and of the 3% of adults who are reported to have IgE-mediated food allergy, 25 have self-reported symptoms,11. However, incidence is on the increase and hospital admissions for food allergy in 1998-
Poor growth, failure to thrive, anaemia, irritability, dehydration, hypovolemic shock, anaphylaxis (less common)
2012 have shown a steady rise across most age groups.11 Furthermore, hospital admissions for anaphylaxis in the UK have risen from roughly 1.5 people per 100,000 per year, to up to eight people per 100,000 in 2012.11 In the same vein, in 2015, seven times as many people were admitted to hospital in Europe with severe allergic reactions as they were in 2005.12 This rise in incidence reporting may be partially due to limited understanding of food allergy prior to the 21st century – complications and fatalities due to what we now know as an ‘allergy’ may have been understood to be a completely separate diagnosis at the time. More likely is that a combination of the factors I mention above are in play to some extent. ADULT FOOD ALLERGY PATTERNS
Children tend to grow out of wheat, milk and egg allergies, so, whilst both adults and children can have allergies to shellfish, fish, tree nuts and peanuts, it is unusual for allergies to dairy and eggs to develop for the first time in adulthood. Shellfish is the most common allergy in adults and adults are more likely to develop oral allergy syndrome, which is caused by uncooked vegetables and apples and fruits with stones. Those who have, or have previously had, eczema, hay fever, or asthma, are more likely to have food allergies.13,14 Several cofactors may also make allergic reactions www.NHDmag.com April 2019 - Issue 143
37
CONDITIONS & DISORDERS more intense, such as alcohol consumption, painkiller use, physical exercise and hormonal states, though evidence of this is currently limited.15,16 FOOD LABELLING
According to the UK’s Food Standards Agency (FSA) regulations, there are 14 foods considered to be the most important allergens17 and must be clearly labelled in any prepackaged foods and beverages: gluten, crustaceans, molluscs, eggs, fish, peanuts, nuts, soybeans, milk, celery, mustard, sesame, lupin and sulphur dioxide. Labelling ambiguities cause confusion amongst both outlets and customers, which can lead to unanticipated exposure of allergens, such as ‘flour’ being listed as an ingredient without specifying the type of flour. Terminology can also cause considerable confusion – with variations including: • ‘may contain…’ • ‘manufactured in a facility that also processes . . .’ • ‘may contain traces of . . .’ For an able adult, this can present the same dilemma when buying food whilst living with an allergy, as it would if one were buying food for a child living with an allergy. Recent improvements to labelling regulations have ensured that even non-packaged foods sold in food outlets must have allergen labelling in their immediate vicinity, visible to the customer – and this is being phased in over the next few years. ALLERGY MANAGEMENT
The current advice for those who experience symptoms of food allergy is mainly centred on total avoidance.18 When we consider that many allergies are self- or misdiagnosed, this muddies the waters considerably, as someone who may have an unrelated condition will avoid something that may be a critical food group and source of daily nutrients, such as gluten-rich foods or pulses. Furthermore, for adults who have never experienced an allergy before, it may be difficult to adjust to avoidance, as well as incite feelings of shame or inconvenience in 38
www.NHDmag.com April 2019 - Issue 143
later life. By comparison, children tend to grow to avoid and accept over a long period of time, but in adults, allergies are sometimes seen as self-proclaimed problems, or dietary fussiness, which can make it harder to adjust when in social settings. Other short-term management strategies for mitigating unanticipated or unwilling exposure to allergens include orally or intravenously administered antihistamines, bronchial dilators, steroids and epinephrine emergency injectors, such as EpiPens. However, for non-IgE-mediated allergy symptoms, the patient is restricted to using steroids and avoidance to manage their symptoms. FUTURE THERAPIES AND RESEARCH AVENUES
Whilst current recommendations for management include complete abstinence or injectors only after coming into contact with allergens, future therapies may well include immunotherapy,19 administration of antiIgE antibodies, Chinese herbal remedies (for example FAHF-2 now in clinical trials), as well as the possibility of combining immunotherapy and anti-IgE antibodies to reduce severity of adverse responses.20 Additionally, though research has been concentrated on serious allergies, such as peanut allergy, research is being conducted into the links between vitamin D and risk of anaphylaxis, as well as the role of epigenetic factors in allergy development.21 SUMMARY
Adult food allergy prevalence is on the rise, yet attention in this area is placed on paediatric food allergy, due to the severity and lack of control children have over adverse allergic reactions. The mystery surrounding exactly why we develop food allergies is, as yet, unsolved and this exacerbates the risk of misinformed selfdiagnosis, as well as underestimating risks of food allergy. Adult food allergy patterns differ to those of children and the most common food allergy in adults is from the consumption of shellfish. Current research is delving into the root of allergy and links are being made between various biological and environmental cues.