Eye drops, whether over-the-counter or prescribed, are designed to be sterile and safe for the sensitive surface of the eye. Using old eye drops, however, carries health risks and is discouraged by eye care professionals. The safety of these medications is tied to a strict timeline. Once this timeline passes, the solution may cause serious eye infections or lose its ability to treat the intended condition. This warning applies to all types of drops, from lubricating solutions to prescription formulas.
Understanding the Two Timelines
The safety of eye drops is governed by two distinct timelines. The first is the manufacturer’s printed expiration date, which indicates how long the product remains stable and effective while unopened and sealed. This date typically suggests the drops are safe for one to two years if stored correctly. Once the sterile seal is broken, the printed expiration date becomes irrelevant, and the second, shorter timeline—the “discard after opening” date—immediately takes effect. For most multi-dose eye drops, this post-opening period is usually limited to 28 to 30 days, or sometimes up to three months.
Why Used Drops Become Unsafe
Once a bottle is opened, its sterile environment is compromised, introducing the primary safety risk: microbial contamination. Each time the cap is removed or the dropper tip nears the eye, bacteria or fungi from the environment or lashes can be introduced into the solution. Although drops contain preservatives to slow this growth, these agents are only effective for a limited period, and a contaminated bottle can become a breeding ground for harmful microbes. Contaminated eye drops can lead to severe eye infections, such as bacterial keratitis, which can threaten vision. Additionally, active ingredients can undergo chemical degradation over time, causing the medication to lose its intended potency and rendering it ineffective for treating conditions like glaucoma or inflammation.
Variations by Drop Type
The 28-day rule is a general guideline, but the drop’s formulation dictates its specific safe usage period. Drops containing preservatives, such as benzalkonium chloride, are designed to inhibit microbial growth and can last the full 28 to 30 days after opening. Preservative-free eye drops, often packaged in small, single-use vials, must be discarded immediately after a single use, typically within 24 hours of opening. These drops offer no chemical defense against bacteria and are meant to be sterile for only one application. Prescription drops often have the most stringent discard dates, sometimes shorter than 30 days, due to the sensitivity of their therapeutic compounds.
Safe Storage and Disposal Guidelines
Proper storage maximizes the safe lifespan of eye drops before they are opened. Most eye drops should be stored at room temperature, away from direct sunlight, heat, and moisture, as temperature extremes accelerate ingredient degradation. If refrigeration is required, it will be clearly indicated on the packaging, and all bottles should be kept tightly closed after use. When a bottle reaches its discard date or the solution has changed color, it must be disposed of safely. The best disposal method is to use a drug take-back program or a disposal kiosk. If a take-back option is unavailable, the drops should be mixed with an undesirable substance, sealed in a plastic bag, and thrown into the household trash.