Asthma Relief Articles - Article #11

The Allergy Epidemic

There is an unprecedented allergy epidemic in the Western world that puts the unrealized avian flu crisis to shame, and rivals obesity as a health problem. For some as yet elusive reason, the global incidence of allergic diseases such as food intolerances, asthma, eczema and hay fever is going through the roof in comparatively well-to-do Western cultures. There are only theories as to why this is so. The predominant notion holds that an overly hygienic Western lifestyle -- marked by the availability of everything from indoor plumbing to antibiotics -- has left many of us with immune systems primed to overreact when they finally do stare down an "invader": milk, for instance, or pollen.

Almost 50 per cent of infants today suffer from some form of eczema, and the prevalence of hay fever stands at between 30 and 40 per cent of the population -- a two- to threefold increase in the last few decades. (In 2003, 18.4 million American adults were diagnosed with hay fever, as were 6.7 million children in 2004.) Health Canada estimates that non-food allergies are "the most common chronic condition in Canadians 12 years of age and older."

Children, who have been particularly hard hit, as many as 14 per cent had asthma. Asthma affects about three million people in this country, six out of 10 of whom do not have control of their disease, according to the Asthma Society of Canada. It kills 500 people in Canada each year, 5,000 in the U.S. Meanwhile, the World Health Organization says 150 million people around the world have asthma, and over 180,000 die annually as a result of it.

And that's just one kind of allergic reaction. Estimates suggest that in the past two or so decades, the prevalence of food allergies has risen from less than one per cent of the population to as high as five per cent, depending on the study cited. Food allergies affect some 12 million Americans, resulting in more than 30,000 emergency room visits annually in the U.S., according to the Food Allergy & Anaphylaxis Network. It is estimated that between 150 and 200 Americans die annually from anaphylaxis as a result of food.

Allergic diseases, Health Canada, estimates, cost the Canadian economy $15 billion in everything from emergency room visits to prescribed medications. Compounding the issue is the fact that we have far too few specialists: in 2003, there were only 126 practising physicians in immunology and allergy in Canada, compared with almost 1,000 cardiologists.

Any substance that triggers an allergic reaction is called an allergen: pollen, dust mites, pet dander, mould, food proteins or any one of a vast array of chemicals in the environment. When an allergen is ingested, inhaled or absorbed through the skin, it stimulates the production of an antibody called immunoglobulin E, or IgE. Subsequent exposure can elicit increasingly violent immune responses, as the body mistakenly marshals its resources to attack what should be, by all rights, a harmless substance. Much depends on previous exposure, and just how much allergen the person comes into contact with.

Some IgE antibodies bind to the surface of mast cells, which line the skin, nose, intestines and bronchial tubes, and play a role in fighting parasitic infections. Mast cells also course through the blood. When an allergen enters the body, it binds to the IgE antibody on the surface of these mast cells, and sparks the release of a chemical torrent flush with histamine and prostaglandins, among other immunologically active molecules. This flash flood leads to itching, inflammation, mucus production, bronchial constriction, coughing and wheezing. Tissue damage can be the final extreme outcome.

Anaphylactic shock is the worse-case scenario -- a massive attack on the skin, and respiratory, gastrointestinal and cardiovascular systems. It can be marked by swelling, laboured breathing, circulatory collapse, and sudden death. While food is the most common cause, it can be brought on by insect stings, medicine, latex, even exercise. It is usually diagnosed in childhood, but can develop in adults, too.

In some cases, people grow out of their allergies. In others, it only gets worse. Children with an allergy to either milk or eggs have been shown to sometimes lose their sensitivity to the offending substance over time. That's usually not the case with nuts and seafood, though the thinking here is still evolving.

Our best educated guess at why we get allergies in the first place is known as the hygiene hypothesis. It's widely credited to British epidemiologist David Strachan, who suggested that clean living isn't necessarily good for us. By depriving our immune system of key infections caused by viruses, bacteria and parasites, we fail to develop the necessary tolerance for ordinarily tame foreign particles. In short, the immune system -- underused and spoiling for a fight -- goes ballistic when finally given the opportunity, no matter how slight the opponent.

Support for the hygiene hypothesis comes from several quarters. Poor people living in developing countries, where a viper's nest of infectious diseases still afflicts the population, exhibit a markedly lower inclination toward developing allergies. This holds true even for impoverished communities within polluted urban centres. Supporting evidence comes from a German study of Bavarian farmers, whose stables typically adjoin the farmhouse, says Denburg. It turns out that the children of those who made a living off the land had fewer allergies than did Bavarians who did not farm.

Dirt, in other words, may be good for you. In a similar vein, having a dog in the home from the first day a child arrives has been linked in some studies to a reduced risk of allergy. Multiple siblings who bounce childhood infections off each other also help, as does eating good bacteria known as probiotics, found in, for example, yogourt with live bacterial cultures. Breastfeeding remains controversial. Some research has shown it does not protect against allergies, as has been suggested.

There appears to be such a thing as good dirt and bad dirt. Research indicates that persistent exposure to particulate matter due to automobile exhaust in urban settings increases the risks of developing allergies and exacerbates asthma. Japan is a classic example of industrialization's downside. In the 1930s, hay fever hadn't yet been recognized as a condition in Japan. However, by the 1960s and '70s, 15 per cent of Japanese schoolchildren were showing signs of hay fever. So, in the space of a very short period of time, during which Japan underwent rapid industrialization, the incidence of hay fever skyrocketed.

Other studies suggest that exposure to antibiotics may be to blame. The timelines certainly dovetail: over the past 40 years, as widespread antibiotic use has climbed exponentially, so, too, have allergy rates. But it's more than just guilt by association. In findings presented to the European Respiratory Society in Vienna in 2003, researchers noted that, in a study of 448 children, infants prescribed antibiotics within the first six months of their lives ran 2.5 times the risk of developing asthma as infants who didn't take antibiotics.

It has been noted that antibiotics cause changes to the microbe population in the gastrointestinal tract that may be linked to how the immune system responds to commonly inhaled allergens. Antibiotics knock out bacteria in the gut, allowing fungi to take over temporarily until the bacteria grow back after the antibiotics are stopped. Research indicates that altering intestinal microflora this way can lead to changes in the entire immune system, which may produce symptoms elsewhere in the body.

Food allergy sufferers show some of the most extreme symptoms, which necessitates meticulous attention to proper food labelling. Canada has nine so-called "priority food allergens" that manufacturers are required to name. This list covers the usual suspects -- peanuts, tree nuts (meaning almost all other nuts, such as almonds, pistachios and walnuts), wheat, milk, eggs and fish (which includes crustaceans, such as crab, as well as shellfish) -- but also some more unusual ones: soy, sesame seeds, and sulphites, which are used as preservatives.

As well-intentioned efforts to sanitize the world spread, we do a lot of good, but they may result in unintended consequences as well.

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