Another common symptom of having a sinus infection is having allergies or symptoms of allergies. This is when a person is constantly sneezing, blowing their nose, when their eyes feel itchy, as well as a scratchy throat that causes coughing. So how do you know if it is actually a sinus infection or if it’s due to actual allergies? According allergist Dr. Alan B. Goldsobel who works as an allergist at Allergy and Asthma Associates of Northern California, “It can sometimes be difficult even for doctors to differentiate,” but when they are accompanied by other signs of sinus infections like “an aching sensation and a feeling of fullness in the middle of your face,” along with colored nasal discharge, fever, congestion, aching teeth, pain when you lean forward or life down, chances are that this is due to a sinus infection rather than an allergy.