HEALTHNET

Origin of Other Kinds of Allergy: Food Allergy

Among different kinds of food allergy cases, the most common allergens are milk, eggs, and peanuts. Seafood, beans, nuts and even fruits can also induce allergy reaction.

(Posted on 22 February 2007)

Food allergy is a common disease that affects many people. The syndromes can be life-threatening and patients suffering from food allergy would have greater chance of contracting other allergies or induced diseases. Nevertheless, local studies of food allergy are much fewer than those of other kinds of allergy and also lag behind other western countries. There are only a few researches about food allergy in Hong Kong and even local incidence rate is still unknown.

Severe Cases Causing Death

Among different kinds of food allergy cases, the most common allergens are milk, eggs, and peanuts. Seafood, beans, nuts and even fruits can also induce allergy reaction. The syndromes of food allergy could be of great variety including itching, rash, urticaria, colic, vomiting, and even constipation and hyperactive. Such syndromes are often mild but basically food allergy can be life-threatening.

In addition, although most people would grow out of their food allergy, like milk (on average 5-year-old), eggs (on average 8-year-old), peanuts (18% of the patients will have their symptoms disappeared 3 to 5 years after first reaction), food allergy is kind of the origin of other allergies. People with food allergy would also be more susceptible to other allergies, such as allergic rhinitis, asthma, migraine, otitis media, arthritis, pulmonary hemosiderosis and anaphylaxis. Other overseas research found that about one-third of food allergy patients will have their symptoms intensified after 6 years of follow up.

Incidence on the Rise in Hong Kong

Some scientists pointed out that improvement of hygienic conditions in modern life, and the wide application of vaccines and antibiotics have reduced the demand on infants' immunity reaction towards microbes and parasites, but at the same time intensified the reaction towards other allergens. According to clinical observation at the Queen Mary Hospital, incidence of food allergy is growing in Hong Kong just as the same as other allergies.

On the other hand, many people wrongly believe that they have food allergy and unnecessarily avoid eating certain kinds of food. In fact, even though most people think that allergies are common, with around 10% to 20% of the local population believe that they are suffering from various types of food allergy, the actually prevalence of the disease is much lower. For example, in the survey in West countries found that only 2% and 1.3% of the population have adverse reaction to milk and eggs respectively, while only 0.5% to 1% are allergic to peanuts.

Research to Understand Food Allergy among Local Children

In order to enhance our understanding towards food allergy, the Allergy and Immunotherapy Clinic of Department of Paediatrics and Adolescent Medicine, The University of Hong Kong Li Ka Shing Faculty of Medicine, who accepts case referrals from family doctors and specialists, will be conducting relevant research on food allergy among school children in Hong Kong.

Information from these researches would be very useful for making future strategy of handling food allergy cases. For example, schools in the US and Canada have guidelines for dealing with food allergy cases. But in Hong Kong's experience it shows that most teachers do not know how to handle children with allergic symptom and would only send them to the Hospital. However, immediate treatment within the first 15 to 30 minutes after the allergic reactions appear is very important and delay in treatment may lead to severe outcomes.

Methods for Testing and Treating Food Allergy

There are actually very advanced technologies available for the diagnosis of food allergy in Hong Kong. Doctors can find out the actual food allergens by understanding the patients' symptoms and the history of their disease, in addition to skin test and challenge trial (i.e. the addition of possible allergic food into patients' diet in a safe condition closely monitored by the doctor to identify the true allergen).

Patients can then minimize the chance of allergic reaction and get a better life quality by avoiding those allergens. For patients with more severe allergic reaction, they can bring along and inject Epinephrine, also called adrenaline, as the medication to control severe symptoms.

Other therapies are also developing in overseas countries. For example the US researchers are studying on injecting antigens to patients to reduce allergic reactions. However, its effectiveness need to be further confirmed through clinical trial, and Hong Kong should only consider bringing in such therapies after more evidence on their effectiveness is available.

Source: The University of Hong Kong Li Ka Shing Faculty of Medicine