Seasonal allergies refer to allergic reactions that occur during specific times of year, usually coinciding with pollen seasons. These allergies are caused by an overreaction of the immune system to airborne particles such as pollens from trees, grasses or weeds, which enter the body through the nose and mouth when inhaled. Symptoms can include sneezing, runny nose, itchy eyes, throat irritation, coughing, congestion, and fatigue. Seasonal allergies are also known as hay fever or allergic rhinitis.