Researchers in Auckland, New Zealand say that the number of children with allergies and asthma is increasing around the world and especially among the youngest.

Asthma is responsible for millions of children missing school, ending up in hospital and even dying and though it is known that the underlying cause of the condition is inflammation of the airways, what actually triggers the problem and why some people develop asthma and others do not is still unclear.

However more and more young children now suffer allergic disorders, and all allergies have noticeably increased in the last decade.

Dr. Innes Asher of the University of Auckland and a team of colleagues repeated the survey done for the International Study of Asthma and Allergies in Childhood in 1991, in order to see if there were any changes in the figures.

The team questioned the parents of more than 193,000 children aged 6 to 7 years from 37 countries about the presence of symptoms of asthma and allergies, such as wheezing, in their child.

The researchers also surveyed 304,680 children, aged 13 to 14 years from 56 countries including Brazil, Canada, Great Britain, Iran, New Zealand, South Africa and Sweden and asked the same questions.

All patients in the study were already on a maintenance dose of Symbicort, which combines a corticosteroid with a long-acting beta agonist.

The researchers found that increases in allergies were more common than decreases and occurred more often in the younger age group.

The increases were greatest for eczema in the younger age group and for hay fever in both age groups.

In the older age group, however, where prevalence of asthma had been high, there were some signs of decreases.

The researchers say the findings are relevant for health service delivery in the countries included in the study, as well as providing a basis for understanding such disorders.

They say in almost all centers, there was a change in prevalence of one or more disorders over time which could have substantial public health implications in heavily populated countries.

Many experts believe that asthma is not a single disease, and the increase in allergies needs to be studied to find the causes and cures.

A number of factors, they say, including air pollution, diet, lifestyle and exposure to bacteria in early life, are possibly linked to the rise in asthma and other allergies.

Professor Asher, the lead author of the study, says the rise in prevalence in many countries is “concerning”, especially as allergies often occurred in large population centres.

The study findings were published in the Aug. 26 issue of The Lancet.