Our Allergic Responses: The Hygiene Hypothesis


A lot of us are very sensitive to some substances. We tend to avoid these substances at all costs. Over the years, it seemed that allergic conditions had reduced in occurrence, but it's like we were wrong. Decades ago, we appeared to have conquered infectious diseases like tuberculosis, smallpox and measles. Now, what we see is a dramatic rise in allergies. In many countries, the prevalence of asthma is increasing, particularly in the second decade of life where this disease affects 10 - 15% of the population.


Allergic reactions are bodily responses produced within 5 - 10 minutes of exposure to a specific allergen. Asthma is a common allergic response which has been on the increase in the Western world in the past three decades. In an asthma attack, the body over-reacts to harmless substances like pollen, house dust mites. The body treats them as though they were dangerous infections. The airways become inflamed and swollen, thus making it difficult to breathe. In serious situations, asthma can kill.


A recent study has attempted to give an explanation for the recent dramatic rise in allergies. This explanation is known as the "Hygiene Hypothesis". It's like the body's white cells over-react because they have got nothing to do. The white cells become mischievous and naughty, and instead of reacting to harmful pathogens, especially bacteria and viruses, the Immune System starts responding to things like pollen.


There's also much evidence that children who muck in and mix in with other children from an early age are much less likely to develop allergies. Children who go to nurseries before the age of 2 are generally less allergic, and that perhaps because they pick up lots of infections from other children. A lot of us as adults obsessively avoid dirt (Guess dirt may be useful after all) but those infants have no such inhibitions. In fact, everything and anything is worth a lick. Our reaction as adults is to take away dirty toys from children. But perhaps, these children have got it instilled into them by nature. Perhaps, the odd bit of dirt helps in laying the foundation for a healthier future.


Animals, especially wild ones, tend to take this a bit further. Elephants acquire the microbes they need to stay 'healthy' by eating the dung of other elephants. It is like it is in-built into them. This may look unappetizing to us, neither are we likely to encourage our children to do this, but among the microbes contained in the dung is an organism which, surprisingly enough, is now being tested as a treatment for asthma.


Bacteria have been in existence even as old as the origin of man. We have all being taught that bacteria is bad and should be avoided at all costs. But bacteria are certainly not all bad. Bacteria present on our skin, for instance, help prevent against other dangerous infections. Taking this a little bit further, bacteria may help prevent allergies. Present in the soil is a particular bacterium, Mycobacterium vacchi, a close relative of Mycobacterium tuberculosis which causes the deadly disease, tuberculosis. Strangely enough, getting infected by this Mycobacterium vacchi appears to help asthmatics.


This I think is based on the see-saw principle. Stimulating one side of the Immune System can suppress the other side, the naughty side that causes allergies. This idea is still very controversial and we need to wait to see how it unfolds before we get too enthusiastic. However, this approach of treating disease with disease is definitely one that is gaining ground, and would soon transform the study of medicine.

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