Friday 4 November 2011

Lifestyle trigger to allergy epidemics - News Article


The puzzling 20- to 30-year lag between the wave of hayfever that gripped the world and the recent wave of food allergies has experts questioning whether the allergy epidemic is partly driven by an "amplifying effect" across generations.

With alarming food allergies now appearing within months of birth, it suggests the factors driving this new epidemic are operating very early in development, most likely in pregnancy, says leading WA paediatric allergist and immunologist Susan Prescott.

"Every mother provides the first environment for her foetus," Professor Prescott said. "Her immune system directly influences the developing foetal immune function. It is already very clear that allergic mothers directly increase the risk of allergy in their babies, so the dramatic rise in maternal allergy is another compounding factor in the allergy epidemic.

"One question is, 'Has there been another wave of environmental changes that is driving this more recent epidemic?' Or is it that you have got a continuing modernising environment overlaying the maternal allergy itself? So it's not just mum's genetics, it's her expression of disease. If she has got a more inflammatory state, she might have a direct influence on the baby's immune system just by her being allergic."

Professor Prescott said it was almost certain that today's rising allergy to common foods such as milk and eggs, that had been consumed by humans for 1000 years, was directly because of a sudden change in our modern way of life.

It was possibly a yet-to-be- identified damaging combination of environmental factors that had emerged over the past 10 years, she said.

Environmental factors under investigation and suspected of triggering allergy-causing inflammation range from pollutants such as cigarette smoke, traffic fumes and pesticides, to a lack of sunlight, physical activity and fruit and vegetables, and a "too clean" environment.

However, researchers were also starting to wonder if it might possibly be that modern environmental changes that had affected the immune system of the hayfever-prone mother were then further altering the immune gene expression in her developing foetus.

Beginning research into this area, some researchers suspected this "amplifying effect" might be partly the reason why today's alarming food allergy wave was far more severe, seeing babies showing signs of allergic disease within a few weeks of birth and those under one-year-old having life-threatening anaphylactic reactions.

Australia has one of the highest allergy rates in the world. Ten per cent of one-year-olds now have a food allergy and in the past decade there has been a five-fold rise in anaphylactic food allergies in preschoolers.

When this younger generation reaches adulthood, the burden of allergic diseases is expected to increase even more. They are at greater risk of developing hayfever and other allergies.

"The problems we are seeing today, they just did not exist like this in the past," Professor Prescott said.

"We see allergic disease much younger in babies and more severe. We are seeing more cases of anaphylaxis in the under one-year-olds from food. And on top of that, we are seeing that they are less likely to grow out of it than they used to be.

"It is all really adding up to an enormous and growing burden. And we do not know what is in store for this generation as they grow up.

"At this stage, we cannot explain the secondary rise in food allergy and why this has been delayed so long after the asthma and hayfever epidemic. One thing is clear, the environmental pressures that are causing this rise in infant allergy must be acting very early in life, even before birth. And it may be no coincidence that this food allergy epidemic is affecting the children of the hayfever generation."

Based at the University of WA and Princess Margaret Hospital, Professor Prescott's research team had shown how pregnancy changed maternal immune response and that allergic mothers had lower Type 1 responses to foreign foetal antigens compared with non- allergic women.

"This means there are likely to be differences in the 'immune environment' experienced by the foetus, which could influence its patterns of development," Professor Prescott said.

Her team had found that even at birth, allergic children displayed differences in the internal machinery of their T cells, with reduced levels of certain proteins involved in the ability to respond to signals.

"This might hold promise as a possible predictive test, however, prediction is of limited value until we can do something to prevent disease," she said.

Professor Prescott saw the allergy epidemic as a flow-on effect from disturbing the natural balance of our environment. Looking at trying to determine exactly what were the environmental factors driving it, she said it was hard to pin the blame on any one factor.

Increasing "hygiene" had been a lead candidate, she said, but many other factors were known to have immune effects, such as modern environmental pollutants, reduced sunlight exposure and lower vitamin D levels caused by more screen-time and indoor activities and modern dietary patterns which promoted inflammation because of the lower levels of fresh fruits, vegetables, fibre and omega-3 fats.

"There are so many things that have changed and it is very hard to prove which one if any," Professor Prescott said.

"It is most likely to be a combination of factors."

Ultimately, the goal was to help prevent allergic disease through the same pathways - including focusing on the optimal condition in the womb for a developing foetus and the genes that were most vulnerable to environmental effects.

For now, the best advice to pregnant mothers was to avoid cigarette smoke - a definite adverse exposure - and breastfeed for general good health. Food avoidance in non-allergic babies had been scrapped as an allergy-prevention strategy, with current notions being that the immune system learnt a food was harmless by a baby eating it early in life and regularly.
 
More research is needed to confirm this and there are several Perth studies aiming to determine if earlier introduction of allergenic foods such as egg will actually reduce the risk of food allergy. Families interested in participating can contact Professor Prescott's researchers on 9340 8834.

Find Dr Susan Prescott's book "The Allergy Epidemic - A Mystery of Modern Life" on  your Healthy Shelf today.

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