Seasonal allergies, also known as hay fever, are caused by an allergic reaction to pollen from trees, grasses, and weeds or mold spores. Common symptoms include a runny nose, sneezing, itchy eyes, and congestion. While avoidance of allergens is difficult, medications can help control symptoms, including over-the-counter antihistamines and prescription nasal steroids, decongestants, or sprays. Allergy shots are also available to reduce sensitivity to allergens over time.