AUSTRALIANS are now reporting food allergies at a rate higher than any other country, a congress of world allergy experts has been told but scientists are at a loss to explain why children are taking longer to outgrow them and they are rising in prevalence and severity.
An immunologist from the Netherlands, Johan Garssen, said low immune tolerance, environmental factors, infections, diet and air pollution were just some of the suspected causes for the increase, but there was not enough evidence to understand how to prevent allergies occurring or to slow rates.
''If I could answer why this is happening, I would win a Nobel prize,'' said Professor Garssen, who spoke at the Australasian Society of Clinical Immunology and Allergy conference in New Zealand this week. ''The only thing we know for sure is that allergies are a disease due to a disturbance of the immune system but what is causing that disturbance we don't know.''
It is estimated one in 10 Australian children suffer from a food allergy, with many of those allergies remaining until adulthood.
Professor Garssen believes breast milk may influence allergy development through the mother's diet and through indigestible carbohydrates in the milk thought to play a role in immunity.
''For the last 20 years we have been trying to create carbohydrates to add to infant formula that can mimic those found in human breast milk,'' he said. ''We haven't been able to do it yet.''
He was hopeful more money would be allocated to research because of what he described as a ''serious rise'' in life-threatening anaphylactic reactions.
The director of Royal Prince Alfred Hospital's allergy unit, Robert Loblay, said he was treating more allergies as well as more serious reactions.
''This is largely because of very rapidly increasing nut allergies and most anaphylactic episodes that take kids to hospital are from nuts,'' he said. ''Walnuts have now overtaken peanut reactions, we're seeing allergies from foods that never used to be an issue like rice and wheat, plus the reactions are happening in different areas than before, such as in the oesophagus or intestine.''
While children previously outgrew egg and milk allergies by the time they began school, Dr Loblay said over the past decade those allergies had been continuing into teenage years.
He said because obesity and allergy rates began increasing about the same time, it was thought diet might play a role in allergy development, but that was ''just a suspicion''.