Seasonal allergic rhinitis, also called pollinosis, hay fever or nasal allergies, and often also written together as hayfever, is a collection of symptoms, predominantly in the nose and eyes, that occur after exposure to airborne particles of dust, dander, or the pollens of certain seasonal plants in people who are allergic to these substances. When these symptoms are caused by pollens, the allergic rhinitis is commonly known as "hay fever", after the fact it is most prevalent during haying s...

An allergy is a immune malfunction whereby a person's body is hypersensitised to react immunologically to typically nonimmunogenic substances. When a person is hypersensitised these substances are known as allergens. The word allergy derives from the Greek words allos meaning "other" and ergon meaning "reaction" or "reactivity". Reactions can vary from the benign runny nose, to life-threatening anaphylactic shock and death.