The first recorded example of allergen avoidance in the treatment of allergic disorders dates from the 16th century. The Italian physician Gerolamo Cardano (1501-1576) was invited to Scotland by John Hamilton, Archbishop of St Andrews (and brother of the Regent), to give advice on the treatment of his asthma. Cardano recommended that the Archbishop should get rid of his feather bedding, which was followed by a 'miraculous' remission of otherwise troublesome symptoms. The first controlled attempts to treat asthma by environmental manipulation date to the beginning of 20th century. In 1925, the Leopold brothers treated patients with asthma and other allergic disorders by moving them into a dust free room1. Storm van Leeuwen created a 'climate' chamber in The Netherlands in 1927 and demonstrated that asthmatic patients improved when moved from their homes into the chamber2. One year later, Dekker observed that measures aimed at reducing the amount of dust in bedrooms had a beneficial effect on asthma symptoms in patients allergic to house dust. Van Leeuwen wrote2: 'In our endeavours to find the cause of the attack...we utilised the known fact that the environment of the asthmatic patient is, as a rule, of primary importance in determining the intensity and frequency of his attacks'. Nowadays, more than ever, it is essential to address the environmental influences on the increasing prevalence of asthma and allergic disorders.