Can using eye drops too often be bad for you or your eyes?
Short answer, YES!.

I found a couple sources, here and here, that explain why. I’ll try to summarize it below:

Eye drops are used to treat several conditions, including glaucoma, allergies, general redness and dry eyes. Prescription eye drops, of the sort used in the treatment of glaucoma and certain severe allergies, carry explicit instructions on how many to use at a time as well as the total number of eye drops that can be safely used in one day. Similar precautions are included in the packaging of over-the-counter eye drops, such as Clear Eyes® and Visine A.C.® Nevertheless, many people ignore these instructions, using eye drops whenever they feel the slightest discomfort.

Those who have followed the advice of Ben Stein and used eye drops to “get the red out” may be surprised to learn that overuse of these drops can increase eye redness and actually bring about the conditions that they are trying to correct.

Naphazoline, one of the active ingredients in Clear Eyes®, is used in stronger quantities in prescription-only eye drops and treats redness caused by pollen, smog, and other irritants. With overuse, this ingredient can instigate a laundry list of side effects, including dizziness, headache, increased sweating, nausea, weakness, nervousness, decrease in body temperature, and slow heartbeat. The potential side effects from overusing prescription eye drops with other active ingredients are similarly unpleasant, and include vomiting, troubled breathing, and back pain.

Other Possible Side Effects:
Dilation of the blood vessels within the eye gives the appearance of redness on the surface of the eye. Common causes of red eyes include extremely dry air, sun exposure, dust, foreign body and an allergic reaction. Derivatives of the medication imidazoline, antihistamines and corticosteroids are ingredients found in over-the-counter eye drops used to relieve eye redness, burning, irritation and dryness caused by exposure to environmental elements.

Rebound Eye Redness
Rebound eye redness is a side effect of overuse of eye drops intended to relieve eye redness. Imidazoline works as a vasoconstrictor, causing the narrowing of blood vessels. Over-the-counter eye drops work quickly to reduce redness, but do not eliminate the cause of the redness. Rebound redness results because the blood vessels in the eye dilate as the effects of the medication in the drops wears off. Overuse of eye drops to relieve the symptom without correcting the cause sets up a cycle of dependency and misuse. Eye drops should be used only as directed, and are not intended for long-term use. According to MayoClinic.com, when over used, eye drops containing imidazoline can cause permanent redness and damage to the blood vessels in the eye.


Eye Irritation
Some brands of eye drops contain an antihistamine in addition to imidazoline. An antihistamine blocks histamine, a chemical released by the immune system in response to an allergic reaction. Histamine dilates blood vessels. Eye drops containing both an antihistamine and any derivative of imidazoline will relieve redness by constricting blood vessels. MayoClinic.com warns that eye irritation is a side effect of this type of eye drops. Symptoms include watery eyes, headache, and a mild stinging or burning of the eyes. Eye inflammation is a risk for users who wear contact lenses.


Eye Infections
Eye drops that contain a corticosteroid work to reduce inflammation associated with an allergic response, radiation or foreign object. This type of prescription eye drop is intended for short-term use. If symptoms are not relieved in two days, the patient needs to be reevaluated by the physician. According to Drugs.com, bacterial, fungal and viral infections of the cornea are associated with prolonged use of eye drops containing steroids. Prolonged use suppresses the immune system’s normal defensive response and increases the risk of eye infections.

As it turns out, even something as seemingly benign as eye drops can be harmful if overused. The key is everything in moderation! Don’t use eyes drops more than you need to!

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