Hi Dear, Welcome to Health Care Magic Team. Understanding your concern Blood in the mouth most commonly originates from gum tissue that has become inflamed due to periodontal disease. However, just because periodontal disease is the most common cause of oral bleeding does not necessarily mean that a diagnosis of periodontal disease can be assumed, nor does in mean that the blood is originating in the gums. Blood in the mouth could also originate anywhere in the respiratory tract, as well as the upper digestive tract, and could be a sign of serious disease. If you have historically been healthy and you have experienced no recent change in the way you feel, it would be prudent to seek an examination with your medical doctor and your dentist to rule out the usual suspects, which would indeed include your speculative guess of a sinus infection, as well as gum disease. You may start with vitamin - c tablets . because sometimes it occurs due to vit-c deficiency Hope your concern has been resolved. Best Wishes, Dr. Harry Maheshwari