In sleep the body temperature is lowered and the cilia that defend the body do less work, so the dust accumulates. On awakening, the body wants to get rid of that dust and at the same time warm the body. So, especially if one is allergic, the person sneezes and coughs. This certainly warms the body but then a "cascade" starts that is hard to stop. So, to avoid morning sneezing, have hot tea before you get out of bed. This can be from a Thermos or a hot plate, or a loving mate. But it will reduce the morning symptoms. It is better if the bedroom has little dust producing objects: Avoid overstuffed furniture, goosedown pillows, wall to wall carpeting and any perfume or mothflakes or things with an odor. Best to have the bedroom as bare as possible. Use throw rugs you can wash every 6 weeks.