Some of you probably know it. It is a lovely day, warm with the sun shining from a blue sky, but then suddenly out of blue you sneeze violently for one or two times. I have experienced it often when going out in the sun or sitting in the bus when it turns and exposes me to direct sunlight. I wondered if I suffered from some kind of sun allergy, but on the other hand I only sneezed a couple of times max and was then fine. What could possibly be the reason?