The Pattern Difference of Food Allergy in Asia and Western World

The type of diet that one consumes regularly can play a role in the pattern differences in the type of food allergies seen across different parts of the world. In the western world, allergy to egg, cow’s milk, peanut is common. Although these food allergies occur in Singapore as well, the cases are relatively low. Nonetheless, there is a slight increasing trend of peanut allergy cases rising over the past decade, and it remains one of the most common causes of anaphylaxis in children locally.

In Southeast Asia, shellfish allergy is common as consumption is generally high locally. While fish is consumed regularly and commonly in Singapore,an allergy to fish is uncommon. Interestingly, there are certain food allergens that are unique and only seen in Asian population this include food allergies against bird’s nest, royal jelly, buckwheat, chickpeas, and chestnuts.

Food Allergy in the Young

Food allergy in paediatric group is explained by ‘dual allergen exposure’ hypothesis. This theory suggests that a person’s immune response towards food proteins can differ depending on the first site of exposure during the first year of life. In children with atopic dermatitis, due to an impaired and leaky skin barrier, one may be exposed and sensitised towards food proteins when the impaired skin is in contact with the proteins.

Without intestinal tolerance, one can develop sensitisation and food allergy. Hence, even avoiding consumption of food allergens, one with atopy may still develop food allergy through ‘skin exposure’. On the other hand, if the child is introduced early of food protein through gut absorption, gut immune tolerance may occur, and this may prevent skin sensitisation towards the particular food.

Currently, the European Academy of Allergy and Clinical Immunology (EAACI) advises the introduction of various foods, including allergenic foods, after the age of 4 months to all children regardless of their history of atopy.

Food Allergy in Adult and Elderly

While food allergy is more commonly heard in the paediatric population, older people can develop food allergy as well. The diagnosis of food allergies in the older group tends to be a challenge due to other confounding medical illness as one progresses with age. The occurrence of food allergy in adult is associated with immunosenescence- the ‘aging of immune system’.

While elderly person may have oral food tolerance against allergies in younger days, food allergies can still occur in mid or later part of life. Over time, there is deterioration of general immune system with a shift of the body towards pro-inflammation. Furthermore, the gut becomes ‘leaky’ and more permeable as one ages allowing food protein/allergens to pass through the gut barrier into the body easily. Also, with age, the digestive ability may decrease, leading to more undigested protein in the gut that can potentially become an allergen.

Repeated insult to the intestinal lining with infections, unhealthy diet, medications, alcohol, smoking can have a long term impact to the gut microbiome, increasing risk of food allergy. Lack of certain micronutrients such as vitamin D, zinc, iron can be associated with pro-inflammation of the immune system, increases sensitization against food particles in older person.

Why having a self-diagnosed restricted diet may not be the way forward for food allergy?

The concern about the topic on ‘food allergy’ is one may wish to prevent ‘allergy’ by omitting out the common food that can cause allergies. A lot of time, the ‘idea about having allergy’ is either self-diagnosed, or childhood ‘hearsay’ without proper diagnosis or medical review, leading to unnecessary avoidance of ‘allergic food’. This can lead to long term nutrient deficiency, stunted growth/ development, or even ironically increase susceptibility of food allergies later in life (when one is exposed to the food allergens later in life).

If you have concern of food allergy, it may be prudent and beneficial to discuss with your health care provider or allergist on your symptoms.

Food Diversity Reduces Risk of Food Allergy

Early exposure to a wide myriad of food proteins and antigens can help the immune system to become tolerant against the food proteins. Food protein may have anti-inflammatory effect and reducing immune reaction against allergens. When a person is consuming a wide variety of diet, one will have a wide range of healthy gut microbiome, building up resistance and immunity against allergies.

In theory, if diet diversity is introduced early in life (during the first year of life), it can potentially prevent allergies.

Good Gut Microflora Reduces Occurrence of Food Allergy

Gut microbiome can function as the gut 'gatekeeper' against noxious external pathogens and allergens. Healthy gut microbiome plays a vital role in immune tolerance against food allergens.

Gut lactobacillus may have a role in improving the gut flora and reducing food allergy though the clinical evidence remains limited. The pregnancy days and early infancy days are believed to be the time that can determine gut microbiome pattern and immune tolerance in later life. Healthy lifestyle (pregnant mother and young children) with balance diet packed with fibers, antioxidants, vitamins, good fatty acid helps to build a resilient gut microbiome and immunity, reducing immune system dysregulation and food allergy in later life of the infant.

What are the common symptoms of food allergy?

Mild food allergy symptoms can present in a subtle way with association with recurring gastrointestinal symptoms such as indigestion, bloatedness, diarrhoea, vomiting and one can be confused with other gastro medical conditions.

Other food allergy symptoms include

Localised lip/mouth symptoms:

Itching and swelling of the lip, mouth, throat
Cough
Hoarse voice
Difficulty to swallow

Symptoms can also involve other organ parts:

Respiratory symptoms

Breathing difficulty
Wheezing
Shortness of breath
Runny nose
Watery eyes

Gastrointestinal symptoms

Vomiting
Diarrhoea
Abdominal pain
Bloatedness

Skin symptoms

Hives
Eczema
Skin itch

In severe acute food allergy, one can have a catastrophic event known as anaphylaxis. This is a dangerous generalised allergic reaction whereby one can feel sudden closure of the airway, inability to breath, feeling faint, wheezing, whole body rashes, and feeling impending loom. One should seek medical attention immediately as it is a reversible condition, and one can succumb following the delay in allergy treatment.

What should I do if I suspect I have food allergy?

If you have concerns of possible food allergy, you should consider consulting your healthcare professional. Food allergy can be diagnosed with a good history of exposure to particular food substance and correlation to your symptoms presentation. Having said that, in real world, due to the consumption of various food particles, identifying the food trigger to allergy can be a daunting and confusing task.

Diagnostic options below can be used in conjunction with the history of exposure to nail down the diagnosis of food allergy:

Skin Prick Test: A qualitative method to measure the reaction of food allergens that are introduced onto the pricked skin surface.
RAST blood allergy test: A quantitative method to measure the antibody in your blood serum against a particular allergen.
Food challenge test: Under proper supervision and potential resuscitation facilities, small amount of possible food trigger is consumed to look out for any potential reaction. This is usually done in hospital setting.

What is the treatment for food allergy?

The mainstay of preventing a particular food allergy is via avoidance following careful evaluation and confirmation of food allergens with your doctor.
In mild food allergy, antihistamine, steroid are commonly used to alleviate and manage symptoms.
In those who presented with food anaphylaxis, it is paramount to avoid the particular food trigger. If avoidance is difficult and impractical, one should consider carrying adrenaline injection/epipen to reverse the allergy when symptoms occur.
Prenatal intake of peanut, milk, wheat (allergenic food) can be considered to reduce risk of allergy conditions in baby/early childhood.
Breast feeding is still recommended even in higher risk allergic babies due to health benefits from breast milk.
Introducing of solid/ complementary food to all infants, weaning from breast milk is recommended at 6-months post-partum based on World Health Organization (WHO) guidelines.

Take home message

We now understand that food allergy is not merely just due to genetic predisposition.
Both young and old population can develop food allergy.
Food allergy can occur in both western world and Asian population.
Environmental factors such as gut microbiome, nutritional status, exposure to food allergen during younger days can affect a person’s predisposition towards developing food allergy.
Food diversity, especially early introduction during the first year of life may reduce the risk of developing food allergy
Healthy diet rich in fibers, zinc, vitamin D, iron, and other micronutrients allows a conducive gut microbiome, leading to better intestinal lining integrity and immune tolerance, reduce susceptibility to food allergy
Allergy tests can be considered to aid diagnosis and evaluation of food allergy.

If you’re experiencing symptoms or simply seeking clarity about food allergies, our doctors at Dr. Ben Medical Clinic are here to help. Book a consultation for thoughtful, personalised care tailored to your needs.

References:

Spolidoro GCI, Azzolino D, Cesari M, Agostoni C. Diet Diversity Through the Life-Course as an Opportunity Toward Food Allergy Prevention. Front Allergy. 2021 Sep 24:2:711945.
Lee AJ, Shek LP. Food Allergy in Singapore: opening a new chapter. Singapore Med J. 2014 May;55(5):244–24.
Lee, B.W., Shek, L.PC., Gerez, I.F.A. et al. Food Allergy--Lessons from Asia. World Allergy Organ J. 2008; 1, 129–133.