You might have thought that health specialists would closely monitor the prevalence of allergies in the population, especially when they are far more common than they used to be. In fact, it happens less than you would think. For asthma, for example, the government publishes statistics on the numbers of people that are admitted to hospital or die from the condition, but it does not publish a running total of how many people are affected overall.
The University of Aberdeen is one of very places that does regularly publish data on childhood asthma, eczema and hay fever, going back as far as 1964. Though we only survey what is happening in the city, the figures are closely watched because they have a very good record of predicting the incidence of these allergies across the rest of western Europe.
When we published our five-yearly report on July 29, it showed that childhood prevalence of asthma had fallen by a third to around 20% following a long rise over decades. Reasons are likely to include improved air quality, reduced smoking, changing diets and improved diagnosis.