What is Hay Fever? Clinically known as Allergic Rhinitis , hay fever causes highly disruptive cold-like symptoms, including a runny nose, itchy eyes, congestion, and frequent sneezing. Myth Buster: Unlike the common cold, hay fever is not caused by a virus. It is an allergic reaction to indoor or outdoor allergens like airborne pollen or dust mites. And despite the historical name, you don't have to be exposed to actual hay to get it, nor does it cause a fever. Symptoms Symptoms usually start almost immediately after physical exposure to the offending allergen: Runny nose and severe nasal congestion. Watery, intensely itchy, and red eyes (Allergic Conjunctivitis). Frequent sneezing and coughing. Itchiness in the nose, roof of the mouth, or back of the throat. Allergic Shiners: Noticeably swollen, blue-colored skin under the eyes caused by restricted blood flow in the sinus cavities. ...