Before buying any type of eye drops, it is important to talk to your doctor so that they can diagnose your issue. In some cases, OTC eye drops are enough, but in other situations, you may need prescription eye drops.

When solving your problem with OTC eye drops, you should know that there are drops that contain preservatives and others that do not. Preservative-free eye drops are generally safe for most people — including pregnant women. Drops with preservatives should be used more conservatively because they may worsen in some cases. The same is true for other drops, such as for redness relief.

“Poor quality artificial tears, or those that say red, often contain chemicals that can cause problems including rebound redness, dilation of the eyes, corneal toxicity, blurred vision and worsening of dry eye disease,” warns Koetting.

dr. Edmund Farrisan associate clinical professor of ophthalmology at Mount Sinai, added that these preservatives have the ability to change parts of the eye. He said, “preservatives in most drops can change the surface of the cornea and cause the loss of these superficial corneal cells, which can eventually lead to more symptoms.” So if you regularly use these types of drops, this could be an issue.

Some signs to look for if you think you’re having a negative reaction to the eye drops include worsening redness, irritation, blurred vision and a burning or stinging sensation. This usually happens because of the preservatives found in some drops. Koetting says that if these symptoms do not improve, it may indicate an allergy or sensitivity to the drops. “However, if a person notices that they have an increase in itching, swelling around the eye or the whites of the eyes become swollen and red, they should stop the drops immediately and call an eye care professional,” he added.