Food Allergy in Singapore: Is there a problem?

Dr Chiang Wen Chin, Associate Consultant, Paediatric Allergy, Immunology and Rheumatology, Department of Paediatrics, KK Women’s and Children’s Hospital

An adverse reaction to a food can be the result of either a food allergy or a food intolerance. Many people think these two terms mean the same thing, but they do not. A food allergy occurs when the immune system mistakenly believes that a food is harmful. In its attempt to protect the body, it creates specific immunoglobulin E (IgE) antibodies to that food. The next time the individual eats that food, the IgE antibodies sense it and signal the immune system to release massive amounts of chemicals and histamines. These chemicals trigger allergic symptoms that can affect the respiratory system, gastrointestinal tract, skin, or cardiovascular system. A severe allergic reaction is called anaphylaxis. A food intolerance does not involve the immune system. Lactose intolerance is a common example. A person with lactose intolerance lacks an enzyme that is needed to digest milk sugar. When the individual eats milk products, symptoms such as gas, bloating, and abdominal pain may occur.

Peanut related food allergy has been an active area of research in most ‘westernised’ countries. The increased prevalence and severity of peanut hypersensitivity appears to be on the rise in the last two decades in some parts of the world. Sequential birth cohorts suggests that the rate of peanut allergy in some countries could be doubling,^(1;2). However, little is understood about how ethnicity and environment may impact food allergy outcomes. Peanut allergy has been perceived to be low in prevalence in Asia. However, sensitisation patterns in children presenting with symptomatic food allergy to the Allergy Clinic at the KK Children’s Hospital suggests that peanut sensitisation is the third most common symptomatic food allergen, and is present in 27% of our Asian patients presenting with food associated hypersensitivity,⁽³⁾. Anecdotal observations that Asian immigrants in North America and Europe,^(4;5) have equal or even increased rates of food hypersensitivity, poses a worrying possibility that with the urbanisation and westernisation of Asia, this increase in the rate and severity of food hypersensitivity will expand to areas of the world where the general awareness of food allergies is relatively low.

Diagnosing a food allergy requires a history of the symptoms that resulted and their duration after eating, the food or foods eaten prior to the onset of symptoms, the amount of each food eaten, and whether similar reactions have occurred before. Symptoms typically appear within minutes to two hours after a person has eaten the food he/she is allergic to. Symptoms of food allergy can include: a tingling sensation in the mouth, swelling of the tongue and throat, rash, eczema, hives, vomiting, abdominal cramps, diarrhoea, wheezing, difficulty breathing, drop in blood pressure, loss of consciousness and (very rarely) death.

There are two tests most commonly used to begin to determine if an allergy exists—a skin prick test or a blood test, such as a specific CAP ELISA (enzyme linked immunosorbent assay). Both of these tests can only indicate whether IgE is present. Therefore, the allergist may combine the test results along with the medical history to make a food allergy diagnosis.

In a recent study carried out in KK Hospital, a questionnaire was sent out to 62 Asian patients with peanut sensitisation documented on skin prick testing when they presented for review of their symptomatic food allergy. Two-thirds of these patients were reported to have had an accidental peanut encounter. The prevalence of repeated reactions secondary to ‘accidental peanut ingestions’ after the diagnosis of peanut allergy/sensitisation was more than 50%, with half of these reactions reported to be more severe than the first symptomatic food reaction. This alarmingly high rate of “accidental exposure” is most likely secondary to both the ubiquitous presence of peanuts in our daily living and peanut seasoning within the Asian cuisine. There is a relative deficiency in public awareness and education concerning the potential grave effects, morbidity and mortality of food allergy and the almost universal absence of appropriate labelling of food components in the Asian culture.

The low use of epinephrine in the Emergency care setting and the low rate of patient awareness of the correct use of the Epipen as seen on questionnaire responses in our population of children poses a challenge to treating this potentially life threatening scenario. As noted with previous other publications, risk of accidental ingestion of peanut allergic patients is high, ranging from 50-86%,^(35;40).

A worrying trend is revealed by the relatively high prevalence of peanut hypersensitivity, now constituting almost a third of patients presenting for the diagnosis and treatment of food allergy in KK Hospital, Singapore. Both the clinical characteristics and peanut protein specific allergen determination suggest a phenotype that is similar to that of European and North American patients, although of less severity. Efforts must be made to educate our population and to increase the awareness of food allergy and its treatment, especially in the use of Epipen in the case of anaphylaxis. A major revision of labelling laws and regulations is also urgently needed in Asia.

References

1. Grundy J, Matthews S, Bateman B, Dean T, Arshad SH. Rising preva lence of allergy to peanut in children: Data from 2 sequential cohorts. J Allergy Clin Immunol 2002; 110(5):784-9.
2. Tariq SM, Stevens M, Matthews S, Ridout S, Twiselton R, Hide DW. Cohort study of peanut and tree nut sensitisation by age of 4 years. BMJ 1996; 313(7056):514-7.
3. Chiang WC, Kidon MI, Liew WK, Goh A, Tang JP, Chay OM. The changing face of food hypersensitivity in an Asian community. Clin Exp Allergy 2007; 37(7): 1055-61.
4. Beyer K, Morrow E, Li XM, Bardina L, Bannon GA, Burks AW et al. Effects of cooking methods on peanut allergenicity. J Allergy Clin Immunol 2001; 107(6): 1077-81.
5. Cataldo F, Accomando S, Fragapane ML, Montaperto D. Are food intolerances and allergies increasing in immigrant children coming from developing countries? Pediatr Allergy Immunol 2006; 17(5):364-9.