Since the 1960s, the prevalence of so-called "atopic" diseases, such as allergies (to pollen, certain foods), asthma and eczema, has doubled every ten years in industrialized countries. Fifty years ago, 5% of the population suffered from these conditions, compared with 35% today. Why is this? Director Marie-Monique Robin interviewed some twenty leading researchers. Tari Haahtela, a pioneer in research into the causes of the dramatic increase in inflammatory diseases, conducted a twenty-year comparative study in the Finnish province of North Karelia, where the way of life was westernized after the Second World War, and in the neighboring ex-Soviet territory of the Republic of Karelia, where subsistence family farming has long dominated.