> One common explanation from doctors—and people in forums who say they are doctors—is that we may be exposing ourselves to specific irritants at around the same time every day. Maybe we walk outside every morning and pollen gets up our noses, or we are always in a particularly dusty room at 4:00 pm. I, for better or worse, tend to spend almost the entire day at my desk, so unless an irritant is traveling to me every afternoon, I'm not sure that explanation pertains to me.
Sun starts shining in through their window at about the same time every day? Many people have sneeze reflex to strong light.