Scientists from the Institute of Epidemiology in Neuherberg, Germany,examined the effect a dog would have on the immune system of childrenfrom birth to six years. The study used data of 9,000 children fromcohorts of infants born between 1995 and 1999 in four German cities.
Lead author Dr Chih-Mei Chen said, 'Children who have a pet dog at homeup to the age of one are 50 per cent less likely to developsensitisation against common inhalant allergens at age six. But no oneknows why.'
Dog ownership is associated with a higher level of endotoxins, which arenatural compounds found in bacteria. Higher exposure to endotoxins inchildhood has been found to reduce the risk of developing allergicsensitisation and disease.
'People thought that because dogs go out a lot they bring in endotoxinsthat act as a regulator for the child's immune system. But in this studywe found this protective effect could not be attributed to this,' saidDr Chih-Mei Chen.
Another study done by Columbia University, New York, assessed the impactof street trees on the prevalence of asthma in four- and five-year-oldsfrom 42 health service districts of New York City.
The researchers calculated the rate of asthma among children related tothe number of trees in their area. They found that for every additional343 trees per square kilometre, asthma rates fell by a quarter, evenaccounting for pollution, population density and levels ofaffluence.
The study concluded that trees might help curb asthma rates by improvingair quality, and children might feel encouraged to play outside whenthere were more trees.
Childhood asthma in the USA rose by 50 per cent between 1980 and 2000,with a high prevalence in poor, urban communities.
Further information:
'Dog ownership and contact during childhood and later allergydevelopment' is published in the European Respiratory Journal. 'Childrenliving in areas with more street trees have lower prevalence of asthma'is published this month in the Journal of Epidemiology and CommunityHealth.