One public environmental concern arising in the USA and Europe during the last decades is the increasing amount of ‘confined animal feeding operations’ or CAFOs. They are important for rural communities and the farming industry in order to produce meat more efficiently. But they might have a negative side effect: their unpleasant smell might hinder neighbours to dry the laundry outside the house or simply might reduce the joy of having a cup of coffee in the garden. Furthermore, they might have negative effects, especially on respiratory health—especially asthma-like symptoms and chronic bronchitis—as it is known from studies focusing on the farmers and farm workers.1 Endotoxin seems to be one of the main ‘bad boys’ in this setting. However, there is also considerable evidence showing that exposure to endotoxins might protect from respiratory allergies and asthma.2

Up to now, a small number of …