Saline is typically the main ingredient in eye drops, according to WebMD. Eye drops contain active ingredients that vary, based on their purpose. For example, eye drops that are manufactured to relieve redness may list vasoconstrictors, such as tetrahydrozoline HCL, naphazoline HCL or phenylephrine HCL as the active ingredient.
Non-prescription eye drops that soothe general dryness and redness are available over the counter, and some specialized eye drops are also available without a prescription. For example, eye drops made specifically to treat allergy symptoms can be purchased in both prescription and non-prescription strength. Active ingredients in allergy eye drops can include emedastine difumarate, azelastine hydrochloride and levocabastine, explains WebMD.