My Husband Is A Very Active 74 Year Old Male

My husband is a very active 74 year old male who today has experienced a flushing sensation and a feeling of faintness 3 times. He is not on any medication for high blood pressure or elevated cholesterol which are both normal.
He has made an appointment with his for tomorrow morning but is wondering what might be causing this sensation. I observed that his face appears flushed when this occurs. This has never happened before today.