Surpringly, perhaps, the obsession with the danger of germs is thought to have led to an increase in various health problems. Much of this obsession with cleanliness seems to be driven by the media and advertising. Headlines about killer bugs, and advertisements that claim their products kill even more germs have led many to buy more and more products to wipe out these dangerous enemies. But current thinking among some researchers and doctors is that a certain level of dirt is good for us particularly during infancy and early childhood when the immune system is maturing. This is known as the hygiene hypothesis.
The incidence of auto-immune diseases like type 1 diabetes and allergies has risen dramatically in developed countries over the past fifty years. The reasons for this trend are not fully understood but it may be related to a rise in hygiene standards. According to this theory, eliminating bacteria in food and the environment of infants may be depriving the immune system of the stimulus it needs to develop adequately, especially during the first critical years of childhood.
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An EU-funded project, called Diabimmune, has set out to test the hygiene hypothesis. Finland and its neighbouring countries are an ideal place to do this, according to the project director, Mikael Knip, professor of pediatrics at the University of Helsinki Children's Hospital. Finland has the highest incidence in the world of type 1 diabetes. Across the border in Russian Karelia, standards of living and hygiene are significantly poorer than in Finland, and the incidence of the disease is six times lower. To the south, in Estonia, a country with an intermediate standard of living and hygiene, the incidence is just under half that of Finland. Nowhere else in the world is there such a contrast in the same geographic area. So this study gives some preliminary support to this hypothesis.
Another study (published in the journal Evolution, Medicine and Public Health in 2013) has suggested that people living in industrialised countries may be more likely to develop Alzheimer's due to greatly reduced contact with bacteria, viruses and other microorganisms. The research has found a "very significant" relationship between a nation's wealth and hygiene and the Alzheimer's "burden" on its population. High-income, highly industrialised countries with large urban areas and better hygiene exhibit much higher rates of Alzheimer's. Using 'age-standardised' data -- which predict Alzheimer's rates if all countries had the same population birth rate, life expectancy and age structure -- the study found strong correlations between national sanitation levels and Alzheimer's.
Swedish researchers at the Sahlgrenska Academy, University of Gothenburg, report that a simple habit may give significant protection against allergy development, namely, the parental sucking on the baby's pacifier. In a group of 184 children, who were followed from birth, the researchers registered how many infants used a pacifier in the first 6 months of life and how the parents cleaned the pacifier. Most parents rinsed the pacifier in tap water before giving it to the baby, e.g., after it had fallen on the floor. However, some parents also boiled the pacifier to clean it. Yet other parents had the habit of putting the baby's pacifier into their mouth and cleaning it by sucking, before returning it to the baby.
It was found that children whose parents habitually sucked the pacifier were three times less likely to suffer from eczema at 1.5 years of age, as compared with the children of parents who did not do this. When controlled for other factors that could affect the risk of developing allergy, such as allergy in the parents and delivery by Caesarean section, the beneficial effect of parental sucking on the pacifier remained. Pacifier use per se had no effect on allergy development in the child. Boiling the pacifier also did not affect allergy development in a statistically proven fashion. No more upper respiratory infections were seen in the children whose parents sucked on their dummies, as compared with the other children, as evidenced by diaries kept by the parents in which they noted significant events, such as infections.
Saliva is a very rich source of bacteria and viruses, and the researchers believe that oral commensal microbes are transferred from parent to infant when they suck on the same pacifier. When the composition of the bacterial flora in the mouth was compared between infants whose parents sucked on their pacifiers and those whose parent did not, it was found to differ, supporting this hypothesis.
T-helper cells in the immune system direct the immune system reactions. In pregnancy the T-helper cells that attack invaders directly without producing antibodies are downplayed as these could lead the mothers system to reject the foetus. This means that the T-helper cells, which are responsible for antibody reactions, are more prominent. These are the ones that are involved in allergic reactions. The new baby’s immune system has the same emphasis as the mother’s had during pregnancy. It is believed that the exposure of the very young to some level of dirt is beneficial in that it rebalances the immune system to emphasise the T-helper cells that are not involved in the allergy process. In an excellent – but very old - article (New Scientist July 18th 1998) Garry Hamilton talks about the gentler side of germs. If the young are not exposed to dirt, the immune system does not go through this rebalancing process, and a tendency to allergy can result. Linda Gamblin in The Allergy Bible cites several medical research projects, which support the idea of allowing children to be exposed to dirt and minor infections to help protect against allergies.
Copyright 2014 Jane Thurnell-Read