Hay fever, also known as allergic rhinitis, is an allergic reaction that causes symptoms similar to a cold, such as sneezing, runny or stuffy nose, itchy and watery eyes, congestion, and sinus pressure. It occurs when the immune system overreacts to harmless substances in the environment called allergens, such as pollen, dust mites, pet dander, or mold
. Despite its name, hay fever is not caused by hay and does not cause a fever. The allergic reaction involves the release of chemicals like histamine, which lead to inflammation and irritation in the nose, eyes, and throat
. Hay fever symptoms can be seasonal, often triggered by pollen from trees, grasses, or weeds during certain times of the year, or perennial, caused by allergens present year-round like dust mites and pet dander
. The condition can affect quality of life by causing fatigue, poor sleep, and difficulty concentrating. It is not contagious and can be managed through avoidance of triggers, medications such as antihistamines and nasal sprays, and sometimes allergy immunotherapy
. In summary, hay fever is an immune system overreaction to airborne allergens, leading to inflammation of the nasal passages and eyes, resulting in symptoms that mimic a cold but without infection or fever
