As a child (forties) I had never even heard of asthma, and never saw anyone at school wheezing etc. No-one had an allergy either. If they'd all died as babies, which would have stopped them breeding, why then would these conditions become prevalent in later decades? There are no huge figures for neonatal or childhood deaths in those periods. It must be an acquired thing and not congenital. As a teacher all my working life, I saw more and more asthma, until by the eighties nearly every other child came to school with an inhaler. We had adreniline epipens ready for severe allergic reactions. We staff used to wonder why. The main changes to life now are central heating and chemicals in food and the environment. We were bathed only once a week, and kept on the same clothes all that time. There were no synthetic materials, only wool, cotton and linen. We played outside all weathers, and got thoroughly mucky. We ate 'organic' home-cooked food. Do any of these facts give any clues? Maybe.