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China, Taiwan, India and Ethiopia. think that differences in intestinal microflora families. Children born with a later birth order
But why is there such a difference between may play a role in the risk of developing allergic are also less likely to have allergic illnesses.
countries? And why is asthma growing at all? disease by affecting the immune system. One Professor Strachan suggested that families with
Well, the medical community doesn’t really idea is that the rise in antibiotic use may have multiple children are more likely to share
know the answers to all of these questions, but affected microflora, prompting a rise in allergic infections, leading to lower rates of asthma.
there have been several theories put forward. illnesses. The idea of early exposure affecting allergies
fits with another finding about asthma:
What is asthma? Smoking according to some studies children who grow
Asthma is an inflammatory condition of the Another obvious risk arises from smoking. up with pets are less likely to develop it. Early
airways, where the lining of the air passages Smoking amongst adults is not thought to cause exposure to ‘allergens’ from cats and dogs, for
become inflamed. Asthma episodes occur when asthma; it causes a range of other lung diseases, example their hair or skin cells, may be
these airways contract, causing the characteristic notably Chronic Obstructive Pulmonary responsible.
‘wheeziness’ and tightness of chest associated Disease and Emphysema – often misdiagnosed Studies also indicate that growing up in a
with the condition. The airways are narrower, as asthma. However, what is well established is family on a farm lowers the risk of asthma.
and it is harder to both breathe in and out and that if a pregnant mother continues to smoke, Exposure to allergens from animals or from
to exchange fresh oxygen for ‘old’ carbon her child is significantly more likely to smoke. chemicals or pesticides on the farm may be
dioxide. It is often triggered by things that responsible. Alternatively, growing up on a farm
irritate the lining of the lungs. This might Pollution could put you at greater risk of viral infection,
include air pollution, pollen, or dust mites. The jury is out on whether pollution causes so reducing your risk of asthma.
However, other factors, such as exercise, or even asthma. We do know that higher rates of
changes in the weather, may prompt an episode. pollution can trigger asthma attacks if the Newer theories
Asthma is often considered an allergic person already has the condition, but whether it New postulations as to the rise of asthma come
disease. It’s more common in families who have can actually cause the condition is debatable. up almost daily. Amongst the more established
allergies. And the huge rise in asthma has also The fact that asthma is on the increase mostly ar
gone hand in hand with big increases in two in urbanised areas suggests that pollution may circle6
e:
allergic diseases – hay fever and eczema. So, be partly to blame. This is corroborated by
what could have prompted this swell in allergies studies in monkeys that were exposed to higher circle6
circle6
Having your child by Caesarian Section
A presence of smokers in the household
Use of non-steroidal anti-inflammatory drugs
over the past four decades? levels of pollutants, who then developed the
signs of asthma. circle6
And less established are:
Theories behind the pandemic However, this is confounded by the fact that circle6
The use of paracetamol
Theories abound as to what has caused this rates of asthma are much higher in areas that circle6
The use of margarine instead of butter
significant and sustained rise, and most of them have been officially certified as having clean air circle6
The use of mobile phones!
Challenges for the future
are related to how our patterns of life have – perhaps only a marker of greater affluence The rise in asthma and allergies remains a
changed, including where we choose to live, and access to diagnosis? puzzling conundrum for the medical and
what we choose to eat, and the lifestyles we scientific community. While looking at trends
choose to adopt. The hygiene hypothesis around the world helps to shed some light on
In 1989, a researcher called Professor David the mystery, we can’t explain it yet.
Diet Strachan came up with one of the most well However, what we do know is that asthma
One such theory centres around dietary change. known ideas to explain asthma trends – the affects more and more of us in everyday life.
As the 20th century progressed, the diet in ‘hygiene hypothesis’. His idea rests on the Increasing numbers of parents will have their
English speaking ‘westernised’ countries has concept that allergic diseases such as asthma, child diagnosed with the condition, and parts of
come to contain less and less fruit and hay fever and eczema can be prevented by the world that were traditionally protected from
vegetables. At the same time asthma rates have catching viral infections in early childhood. this disease are now exposed.
risen in the same places. Could they be related? Professor Strachan suggested that as general The economic and health burden this places
Well, the link between diet and asthma is far household standards and personal hygiene on medical communities and health
from proven, but some studies do at least improved throughout the 20th century, children organisations on a global scale adds to the
suggest an association. For example, one piece were exposed to fewer viral infections, and that challenges that we already face, and we need to
of research showed that eating foods containing this caused more allergic conditions. understand the causes better before we can
vitamin E was linked with lower asthma rates. Although it isn’t known exactly why this really tackle them.
Another found decreased levels of asthma might happen, researchers think that early
among fish eaters. Another unconfirmed theory infections might modulate the immune system
to explain the rise of asthma centres around in some way to prevent allergies developing.
intestinal microflora. Intestinal microflora are The hygiene hypothesis was based, in part, Dr Sneh Khemka, MBChB MRCOphth
the millions of bacteria that naturally grow upon the observation that allergic diseases are Medical Director
inside the digestive tract. Some researchers less common in larger families, less affluent Bupa International
June 2009 Investment International www.investmentinternational.com7
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