Allergies need to become a medical discipline in Hong Kong

Allergy incidence in Hong Kong is somewhere in the middle of the international league table. But unlike most established urban centres, in Hong Kong it appears to be rising - something the city's medical services might increasingly struggle to cope with, given that there's no formal medical training for allergy specialists here.

Allergies affect up to 40 per cent of people globally, according to the World Health Organisation, and the rate is on the rise, particularly in industrialised nations. They occur when the body mistakes a normally benign substance for a toxic one, triggering the release of an antibody called immunoglobulin which affects white blood cells, provoking an inflammatory response.

Usually, that response is just uncomfortable. The most common is allergic rhinitis, which causes sneezing and a runny nose. Other unpleasant possibilities include allergic asthma, causing wheezing, coughing and shortness of breath; blocked and painful ears; eczema and hives; and stomach ache, bloating, vomiting and diarrhoea.

But allergies can also be dangerous - even fatal. With so-called anaphylaxis, inflammation is so rapid that it can become difficult to breathe, and can also result in dangerous drops in blood pressure and heart attacks.

There are many potential allergens. Among the most common is foodstuffs; in particular, nuts, seeds, milk, eggs, soy and shellfish. Commonly self-diagnosed food intolerances such as lactose and gluten aren't in fact allergies, and involve different physical responses to the unwanted substance.

Other top allergy offenders include pollen; insect stings; animal dander; house dust mites; medications, especially aspirin and antibiotics; and substances that come into contact with skin, such as latex, metals (mainly gold, cobalt, nickel and chromium), mould, perfume, formaldehyde and semen. Some exceptionally unlucky people are allergic to water. Naturally, symptoms vary by allergen. Plant pollens cause you to sneeze, and food allergies cause all manner of unpleasant gastrointestinal effects.

As with most places, rhinitis is the most common form of allergic response in Hong Kong. But its most common cause is different here. Most allergic rhinitis around the world is seasonal, triggered by pollen and known as hay fever. But in Hong Kong, the city's predominantly urban environment means people come into less contact with pollen, and most cases are perennial rather than seasonal.

While the cause is not proven, Dr Terry Hung, an ear, nose and throat specialist at Matilda International Hospital, has no doubt what's to blame. "Airborne allergies are getting more common as the pollution is getting worse," he says. "As there are more pollutants in the air, people are exposed to more allergens."

Dr Lee Tak-hong, head of the new Allergy Centre at the Hong Kong Sanatorium and Hospital, recently returned to the city after spending most of his professional life in Britain. He says he's noticed quite a few differences here.

"I've always felt that food was important here, and I've seen a lot of food allergies, especially in young babies. It's very obvious to me that there are a lot of issues here with artificial flavourings and allergies. Unfortunately, with a lot of Chinese food, there's no research as to what's actually in it, so diagnosis can be challenging."

Frank Wong, chairman of the Hong Kong Allergy Association, says that labelling of allergens on food packaging is actually mandated under the Food Safety Ordinance introduced earlier this year, but so far has not been widely enforced.

There has been only one product recall to date because of the presence of an unlabelled allergen. In the United States and Australia, he says, there are on average about 100 recalls a year.

"Either we're doing so well, and our manufacturers and importers are so stringent, or the government is not doing its work and we're not noticing." But recent incidents involving Chinese products exported to Australia with unlabelled allergens suggest that the latter is more likely.

In terms of symptoms, Lee says that a far larger number of patients here come to him with eczema than in Britain, and it's often much more severe. There are two main reasons, he says. "One is under-diagnosis, and the other is that people have often gone to seek alternative help, and it's often Chinese medicine. Sometimes it works, but sometimes it doesn't and only then do they come to see me."

Lee estimates that about two-thirds of the eczema cases he sees are caused by food, with milk and eggs by far the most common causes.

Heredity is the most important factor in allergies. Identical twins have the same allergies in 70 per cent of cases and fraternal twins 40 per cent. If neither parent has any allergies, there's a 16 per cent chance of their child having one. If one parent is a sufferer, the odds are between 20 and 30 per cent. If both parents are, it's about 50 per cent. Lee pinpoints three other possible causes for the increase in allergies. One is climate change, resulting in longer, hotter summers, making pollen more abundant. Another is lack of sunlight, with several studies linking higher allergy levels with vitamin D deficiency.

The third is the so-called hygiene hypothesis. This suggests that our bodies are set up to deal with pathogens, but in our over hygienic world we don't get exposed to enough of them. So our immune system starts attacking harmless microbes as if they're pathogens, triggering the allergic reaction.

It seems to be supported by anecdotal evidence. Many allergies are far more common in the developed than the developing world, and in cities rather than rural areas. A recent study from Northwestern University's Feinberg School of Medicine in Chicago found that, in the US, 9.8 per cent of children in cities had allergies, whereas only 6.2 per cent did in rural areas. For peanut allergy, the figures were 2.8 per cent and 1.3 per cent, and for shellfish allergy 2.4 per cent and 0.8 per cent.

A study from Finland suggests that children who grow up in rural areas may have more diverse bacteria in their bodies, and that the absence of certain bacteria appears to be associated with an increased risk of allergies.

There's even a theory that our immune systems are habitually oversensitive because of clean drinking water. The idea is that the parasites routinely present in untreated water secrete immune system suppressants inside us. Because our water would have been unclean until relatively recently, we are said to have developed into symbiosis with the supposed invaders, leaving us dangerously over-sensitised without them.

Allergies are diagnosed by a skin prick test or blood test. But the tests can't usually detect reactions to medications, for example, and can sometimes return false positives because they detect the presence of immunoglobulin rather than an actual allergic reaction.

The best course of action after detection is simply to avoid the allergen, but other possible symptomatic treatments include antihistamines and steroids. An intramuscular adrenaline shot is the usual treatment for anaphylaxis.

For people who can't avoid an allergen and are seriously suffering, another option is immunotherapy, which involves vaccination with increasingly large doses of the allergen, causing tolerance to develop. It's administered either under the tongue or by subcutaneous injection every eight to 10 weeks for three to five years.

Lee favours immunotherapy and says he uses it on patients with allergies to house dust mites, pollen, cat and dog dander, and bee and wasp stings, but Hung only recommends it for patients whose symptoms are debilitating - those with breathing difficulties, or near-constant sneezing. Otherwise, he says, over such a long time scale, the biggest problem is compliance. Plus, there's a small risk of anaphylaxis.

While working in Britain, Lee says it became clear there were far too few trained allergists there, with doctors from other fields stepping in, mainly because they were the ones dealing with the symptoms. That changed about a decade ago, when formal training for allergy specialists was introduced there.

Lee returned to Hong Kong to set up Sanatorium's centre, the first in Asia, this year. He says the situation here is similar to that which Britain faced 15 years ago.

"Dermatologists, ENTs [ear, nose and throat doctors], and so on were treating allergies. All medicine had to be imported, and preventative strategies were not adopted as they should be. Public knowledge of allergies is very poor. That's not unique to Hong Kong. It's the same wherever allergies aren't a medical discipline."

While the HKAA gets government funding, Wong says the political situation has made officials slow to act. "In places like the US and Britain, there have been government organisations working on this for 20 or 30 years. But not here."

healthpost@scmp.com