Posts Tagged ‘allergy epidemic’

`I can’t think of any of our friends where there isn’t at least one member of the family with asthma, and often it’s both children,’ says Dee Gill, a university lecturer from Melbourne, and herself asthmatic. Australia is one of the countries worst affected by the allergy epidemic. ‘If you go to a primary school sports day, you’ll see the teachers going along the line of kids, saying, “Have you taken your asthma medication?” It’s so much a part of everyday life now.’
The word ‘epidemic’ is now being freely used, even by the most conservative of medical scientists. All the classical allergic diseases seem to be on the increase, including:
• atopic eczema – in the United States, up from 3% of children in the 1960s to 10% in the 1990s; in Britain, more than 16% of 12- to 14-year-olds are now affected
• hayfever – extremely rare in the 1930s (26), affecting 3% of children in 1964, and now seen in 18% of 12- to 14-year-olds in many parts of the world
• asthma – the figures for children in one Scottish city are: 4% in 1964, 10% in 1989, nearly 20% in 1994
• peanut allergy has clearly been on the increase since the 1960s; a very alarming UK study shows that rates of allergy to peanuts have doubled in less than a decade (between children born in 1989 and those born in 1996).
To the question ‘why?’ there is no simple answer – the causes are many and various. But one thing is abundantly clear: this is a disease of modern, Westernised society. Travel to rural Africa or
Are other immune diseases increasing?
These two pages deal solely with the classical allergic diseases . Many doctors have the impression that eosinophilic disorders are also becoming more common, and some think that there are more cases of adult-onset coeliac disease than previously.
Asia, among people living a simple subsistence lifestyle, and you will find little or no sign of allergic diseases. There are no words in their languages for asthma or hayfever, because these are virtually unknown.
As soon as these people become more affluent, and change their lifestyle, allergic diseases appear, and the number of cases steadily rises over the years. Sometimes this coincides with a move to the towns, but it can also occur when people stay right where they are – as in Taiwan, where allergies rose dramatically with increasing affluence and a more Westernised way of life.
In the case of asthma, everyone is keen to blame air pollution, particularly traffic pollution. But a look at the research shows the link to be largely a myth. Certainly, polluted air can trigger off attacks in someone who already has asthma – but the effect is not huge, and this is not the same as causing asthma to develop in the first place. And while growing up in polluted air can increase the chances of children developing asthma, it makes only a small difference, one that simply cannot account for the massive asthma epidemic. The hollowness of the pollution argument is spectacularly evident when you consider rural New Zealand, where asthma rates are among the highest in the world, yet there are no factories, and sheep heavily outnumber motor cars.
Allergy to house-dust mites has also received a lot of publicity, and it does play an important part. Our warm, draught-free and thickly carpeted homes allow these tiny creatures to breed with abandon and many people with perennial rhinitis, asthma or atopic eczema have an allergy to dust mites. Recent research shows that dust mites play a far larger role than anyone previously suspected: the dust-mite allergen actually provokes immune cells, and once an allergy to dust mite has begun, other allergies become more likely.
But blaming house-dust mite as the supreme cause of the allergy/asthma epidemic (as some do) is as mistaken as blaming pollution. The proof in this case comes from the highlands of New Mexico where dust mites cannot survive because the air is much too dry. Allergies, including asthma, are just as common as elsewhere in the Western world.
Spoiling the immune system
Thanks to discoveries made during the past decade, we are now beginning to understand what has made the younger generations – those born since the early 1960s – so much more susceptible to allergies. The new data reveal that the way you bring up a child’s immune system matters as much as the way you bring up the child itself. You can ’spoil’ an immune system all too easily, by protecting it from life’s natural challenges and obstacles.
As a small child, I ate a spoonful of soil. My mother was horrified (she was still telling the story twenty years later) but research now shows that she should not have been. Exposure to certain bacteria in the soil, known as mycobacteria, is probably just the kind of education that a young immune system needs. These bacteria cause no 111-health, no symptoms at all, but they are thought to have an effect on the immune system, pushing it away from allergic reactions.
Children playing outdoors have probably always eaten soil, either intentionally or by accident – licking a grubby finger. Country people used to say, philosophically, ‘You eat a bushel of dirt before you die’, and they were probably right. Indeed, you may well need to eat a bit of dirt before you can live happily in an allergen-packed world. Now researchers are trying to make a vaccine using soil bacteria, to simulate this effect.
A study from the University of Bristol shows that children who wash their hands more than five times and have two baths a day are almost twice as likely to get asthma as children who wash their hands less than three times a day and have a bath every other day. The grubbier children are probably being protected from asthma by acquiring minor infections, with few or no symptoms. These infections could include both soil bacteria and germs that are spread from one child to another.
Other research reveals that children with older brothers and sisters are less likely to suffer from certain allergic diseases than only children or firstborn children. This may be due, in part at least, to the spread of infectious diseases, because mixing with lots of
other children in a nursery produces more infections but also gives protection against allergy. Studies from the former East Germany, where sending children to day nurseries at an early age was once the norm, demonstrate that if children from small families went to nursery aged 6-11 months they were substantially less allergy-prone than if they went later. The allergy risk was highest for only children who did not go to nursery until they were over two years.
Researchers in Colorado have recently tackled this subject from a different angle completely, analysing house-dust for the levels of bacterial endotoxin – substances that come from certain kinds of bacteria and which have a powerful effect on the immune system. If the house-dust contained high levels of endotoxin, babies brought up in that house were less likely to give positive skin-prick tests to common allergens such as cats, milk or house-dust mite. The babies from very clean houses, with low levels of endotoxin in the dust, were the ones with allergic reactions. (Fortunately, it is possible to have a dusty house with very little house-dust mite)
The hygiene hypothesis, as it is known, could also explain the strange history of hayfever. For the first century of its existence, hayfever was a disease of the urban upper classes, only gradually working its way down to the poor and to rural communities: this fits in well with the gradual spread of more hygienic ways of life. In most parts of the developed world today, it shows no class distinctions, but recent investigations have found a lower rate of hayfever among children raised on a farm with animals compared to children living in the same villages without farm animals.
In addition to greater hygiene, the following aspects of modern living appear to promote an allergic tendency in children:
• smoking by the mother during pregnancy and after, which may boost IgE levels
• breathing nitrogen dioxide from gas cookers, and formaldehyde from various household sources ; exposure to substances called phthalates, from plastics, may also be important; the poor ventilation of many modern houses, and the far greater time spent indoors aggravates the problem by increasing exposure to these irritants, and to allergens such as house-dust mite and moulds.
• taking antibiotics during the first two years of life
• bottle-feeding and/or abrupt and early weaning
• exposure to a virus called Respiratory Syncytial Virus (RSV) during infancy, which provokes an IgE-reaction (37)
• caesarean births; simply being born in a hospital might also raise the risks by exposing newborn babies to Staphylococcus, which adversely affects the immune system.