I've been using this fairly continuously for about a year. I had no side effects, except that when I first started using it, it washed out a little sinus infection that was in one of my sinuses around the eye. My allergist said that this was actually quite a common occurance. Other than that, I love it. It works really well, and doesn't dry my eyes out. Unlike OTC eyesdrops it is just an antihistimine, it does not have the redness reducers, and it's the redness reducers that can cause excessive dryness.