Possibly has Penguin99, he said it can be caused by anything like house dust or even changes in the seasons that I may be susceptible to, I do sneeze on a regular basis, and always twice! I tend to have a real runny nose too in the summer which could be the pollen, yet I don't have full blown hay fever?
Its all very irritating, but I was reassured it wasn't anything disastrous, just annoying!!