A clean kill

It seems that cleanliness has been overrated

 
Published: Sunday 31 January 1999

-- (Credit: Rajat Baran)h g wells's 19th century vision of a Martian invasion of Earth, The War of The Worlds , saw Earthlings emerging victorious in the end of a lengthy, devastating war through sheer persistence, a will to fight back and those ever-popular human strongpoints -- faith and hope. But outnumbered and outsmarted by the tentacled Martians and their fatal "death ray", humans could do precious little to win this fantasy battle. The Martians lost because of an inherent biological weakness: theirs' was a world where science had got the better of all germs, wiping them out forever. Those same germs, however, were present in the Earth's atmosphere and finally proved an enemy too strong even for the Martian army. Fantasy? Perhaps not.

Scientists say our obsession with cleanliness might prove just as expensive for us as it was for Wells's Martians. And nowhere else does this possibility seem so real as in Japan, a nation traditionally obsessed with cleanliness.

Koichiro Fujita, a leading tropical disease researcher at the Tokyo Medical and Dental University, Japan, says, "We are wasting money, producing germ-free goods, soaps and chlorine-filled water to create a weaker Japan." Already Japan's tap water contains the highest amount of chlorine in the world.

The dangers of such systematic attempts to live in a climate, where parasites of any kind are ruthlessly eliminated, are showing their effects: their obsession with cleanliness has played havoc with their immune systems and has created a new generation of weaklings. Fujita feels that there has been too much publicity that all germs and parasites are harmful.

Graham Rook, immunologist at the University of London, along with Fujita, is an enthusiastic supporter of the so-called 'hygiene hypothesis': during most of evolution, the human immune system was bombarded with dirt and germs and humans lived with them from cradle to death. The human immune system has learnt to make the best of such adverse circumstances, relying on the sophisticated network of chemical pathways and specialised immune cells. Only when humans move away from germs, things start going haywire. This is one reason why there is a rapid rise in asthma in the us , Western Europe, Japan and Australia. Rare only a few years ago, it now affects over 20 per cent of population. This is primarily because the human immune system functions below par if forced to work in a 'barren' environment.

It is not just asthma: hay fever and eczema may be on the warpath too. Further, diabetes is afflicting children across the world at a much younger age. Why allergic diseases followed affluence and modernisation, still remains a mystery. Even after accounting for genes, the incidence is far too high to run in families. Even air pollution may not account for these allergic reactions as they are common in places like southern Sweden which boasts of one of the cleanest environments.

The first hint of the hygiene hypothesis came in 1989 when David Strachan from the London School of Hygiene and Tropical Medicine proposed that kids with older siblings who bring in bucketful of infections somehow helped protect younger children from allergies. In the last two years, more experimental evidence is surfacing that shows the gentler side of germs. Young adults in Guinea-Bissau in West Africa, who, as children, caught measles during a 1979 epidemic were half as likely to have allergies now as they have escaped the disease.

A recent study shows the relationship between auto-immune diseases like diabetes and exposure to bacteria, viruses and infectious parasites. David Philip and his group from University of Southampton have reported that children with insulin-dependent diabetes are less likely to have infections before their fifth birthdays than those without the disease ( Archives of Disease in Childhood, Vol 77, No 4).

Some germs like mycobacteria that are present in mud and water -- about a billion of them are present in a litre of unchlorinated water -- demonstrate how bacteria affect our immune system. Most mycobacteria do not cause disease, exceptions being those causing tuberculosis and leprosy, but they dramatically alter the functioning of our immune systems. Scientists are not saying that one should take some muddy water every day. Hygiene does save lives. But being excessively obsessed to be squeaky clean may not be all that welcome either.

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