There is little doubt that during the last 50 years the incidence of allergies has increased exponentially. You may have noticed that every other person you talk to has some sort of allergy to pets, dust, hay fever or food; and if not their children probably have asthma or eczema. These anecdotal observations are backed up by the statistics which now show that worldwide around a third of people experience some sort of allergy. In the western world these figures are closer to a half, which is pretty shocking particularly when you consider around a hundred years ago allergies were virtually unheard of.
The Allergy Epidemic
Two hundred years ago hay fever didn’t even exist. The first reported case was in 1819 and for the next hundred years it was an extremely unusual medical condition. By the 1960s around 3% of children were diagnosed with hay fever and now the figure is closer to 10%. This increase in allergies is the same across the board; eczema has gone from a rarity to affecting 16% of British children and childhood asthma levels are now at around 20% compared to 4% fifty years ago. It is little wonder the medical world is now calling it the “allergy epidemic”.
A Western Disease
What is particularly striking in the figures is the worldwide distribution of allergies. The UK, Europe, Australia, USA etc top the tables but a similar pattern is emerging in developing countries. However, in societies where people live simple subsistence lives allergies are practically non-existent.
This all begins to change as the standard of living increases with people moving into the towns and adopting a more western way of life. So, which aspect of modern life is it that is driving the increase in allergies?
Whilst it would be easy to assume that pollution from increasing industrialization was the obvious cause the evidence does not support this. It is true that air pollution can exacerbate the symptoms of asthma but it does not appear to cause it. For example rural New Zealand has some of the highest levels of asthma anywhere but the air quality is pristine.
One link that has been made is with our modern home comforts and the increased incidence of dust allergy. Insulation, double glazing, thick carpets and central heating have all helped make our homes a veritable paradise for dust mites. This may have further implications as evidence is emerging that the heightened immune response to dust mites may make sufferers more susceptible to developing further allergies.
The Hygiene Hypothesis
There is growing evidence that the sharp rise in allergies since the 1960s might well be the result of us becoming too clean. By making our children’s environment sterile and germ free their immune systems may not be developing full protection against allergic diseases.
The “hygiene hypothesis” certainly seems to have a good weight of evidence behind it. It would explain why farm children and those from larger, poorer families have a lower incidence of allergy that their wealthier urban counterparts. Other studies have shown that children who wash very frequently are almost twice as likely to develop asthma.
The mechanism for this theory have not been fully explained yet but it would effectively explain why the first cases of hay fever were amongst the upper classes and gradually spread down to the poor as general levels of hygiene increased.
Even if the hygiene hypothesis offers an explanation as to the rise of the allergy, it does not provide a solution. Over the last century improved hygiene has massively improved public health, wiping out illnesses such as cholera in the developed world. It seems like a fine line must be trodden between an over sterile existence and the real danger of infectious diseases.