Experts are warning policy makers that allergic disease might replace infectious disease as a major cause of ill health in cities undergoing rapid demographic changes in developing countries.
New research tracking the number of cases of childhood eczema across the globe has revealed big changes in the prevalence of the condition over the last five to ten years and suggests that environmental factors could be having a significant impact.
Research, by a team of allergy experts across the world, has shown a levelling off in the number of cases of eczema in children aged between 13 to 14 years and a decrease in some countries like the UK and New Zealand where childhood eczema was once highly prevalent. But a continuing rise in younger children aged between six and seven and in the number of cases reported in developing countries is of growing concern.
Their paper, published in the Journal of Allergy and Clinical Immunology, suggests environmental factors are key for eczema expression because it is highly unlikely that genetic factors would change in such a short time.
Hywel Williams, Professor of Dermato-Epidemiology in the Centre of Evidence-Based Dermatology at the University of Nottingham, who led the eczema research, says eczema needs to be tackled at a public health level in many countries.
He says that moderate or severe cases of eczema have a significant impact on family life and carry an economic burden comparable with that of asthma. Constant scratching often leads to sleep deprivation which also affects careers as well as incurring significant financial costs.
Professor Williams and his international team analysed information from two worldwide surveys of asthma and allergy symptoms in children which was carried out by the International Study of Asthma and Allergies in childhood (ISAAC) between 1991 and 2001. ISAAC was formed in 1991 to facilitate research into asthma, allergic rhinitis and eczema by promoting a standardised methodology, and currently holds a Guinness World record for the largest epidemiological study in children.
Professor Williams and his team analysed over 300,000 children aged 13 to 14 years from 105 centres in 55 countries and nearly 190,000 children aged six to seven years from 64 centres in 35 countries.
The largest decreases in children aged between 13 to 14 years were seen in developed countries in northwest Europe, such as the United Kingdom, Ireland, Sweden, Germany and also New Zealand. Professor Williams says this provides some reassurance that an allergic disease epidemic is not increasing inexorably throughout the world, and that a threshold effect may be in operation.
Most of the biggest increases in the 13 to 14 age group were seen in developing countries such as Mexico, Chile, Kenya and Algeria and in seven countries in Southeast Asia.
However, in six to seven year olds most countries showed significant increases over the five to ten year period.
Professor Williams said: “This is the first time we have been able to have a glimpse at what has been happening to eczema symptoms across the world using standardised methods. The results suggest that environmental factors are key to the expression of eczema — if only we could identify those factors so that we could prevent eczema in those countries experiencing significant increases.”
Although no singular environmental or genetic risk factor adequately explains the changes in eczema symptoms described in this paper Professor Williams does have some words of encouragement. He says there is already some evidence that eczema might be preventable to some degree and there is plenty of evidence on effective approaches to managing existing eczema symptoms. The way forward, he suggests, is for all public health responses to the eczema epidemic to ideally include an evaluative component so that others in the world can understand which approaches are more likely to be successful than others in different circumstances.
(Source: Journal of Allergy and Clinical Immunology : University of Nottingham : January 2008)