There are two common causes of itchy eyes: 1. Consider allergies, which may be contact allergies or seasonal allergies. Contact allergies are acute allergies caused by special exposure to gases, food, or medications during a certain period of time. They are often severe and require topical medication in combination with systemic medication to control itchy eyes and congestion. Seasonal allergies are often caused by seasonal dust, or pollen or grass seeds that cause conjunctival allergies, and require the use of topical drops to control the symptoms. 2. Itchy eyes may be caused by the recent heavy use of the eyes or dry eyes, often without white congestion, and the degree of itching is intermittent and not very heavy. This situation requires rest, and can use some artificial tears eye drops, such as sodium glass acid or polyethylene glycol eye drops to relieve, often after 1-2 weeks of rest or use of drops, the majority of people can also relieve the itchy eye situation.