Soon we go again, alder, Hasel already flying, Ambrosie, mugwort, birch, stinging nettle, grasses, Rye follow very soon and allow the pollen to fly. While a lucky few have no problems with the pollen, are just in the industrialized countries, countless people plagued by allergies. But why is that? The following Video made by TED shows us, what happens these days with our immune system.