Early allergen contact low asthma risk
30 September 2004
Exposing young children to allergens such as cat fur and house dust mite does not increase the risk of them developing asthma, suggests a new study.For many years scientists have thought that the likelihood of developing allergic conditions such as asthma is related to the level of contact with allergens early in life.
However, research published today in the scientific journal Thorax casts doubt on this theory, and suggests that genetics and birth order may play more significant roles in the development of asthma.
Scientists monitored 625 children from Ashford, Kent from birth until 5 and half years of age. They measured levels of allergens in cat fur and dust in their homes at the beginning of the study, and each year interviewed mothers about whether their child had experienced wheezing.
At the end of the research period the children were also skin-prick tested to see if they had become sensitised to house dust mite or cat fur allergens.
Only one in ten of the children had become sensitised to either allergen by the age of 5 and a half.
Both sensitisation to allergens and wheezing were significantly more likely if the child's father had a genetic susceptibility to allergy or the child was a firstborn.
The researchers found no clear relationship between levels of allergen measured early in life and sensitisation to those allergens or frequency of wheezing over the next five years. In fact, even when very low allergen levels were measured sensitisation and wheezing were observed.
'The findings from this study, and other recent trials, demonstrate that there is no simple relationship between allergen exposure in early life, sensitisation to allergens and the subsequent risk of developing asthma.' said Dr Matthew Hallsworth, Asthma UK's Research Manager.
'It has become clear that the development of asthma depends on a complex interaction of genetics and environmental exposures, and until we understand more about these processes it is very difficult to give clear advice to concerned parents.'
The study's authors, at the National Heart and Lung Institute in London, concluded that reductions in domestic allergen exposures alone are unlikely to have a major impact in reducing the incidence of allergic sensitisation or wheezing in childhood.
