It seems that your eyes have got some problems. So, in the first place, you need to know that eyelash extension is made up of chemical stuff and could be highly irritated to your eyes, causing some serious problems such as red eyes, watery eyes, as well as other infections. Anyway, you might have got watery eyes from it. Therefore, I recommend you stop using it and consult a doctor for treatment.
Well, generally speaking, it can lead to watery eyes after you have used eyelash extension. First, you should know that eyelash extension is applied directly in your real eyelash with the some chemicals. Also, because they are made from chemical, they can just hurt your eyes, for your eyes can be fragile. What is more, long time using of eyelash extension can carry many bacteria into your eyes. Finally, eye infection, even dry eyes can occur. At that moment, your eyes can be watery. Of course, in some cases, redness may occur too. So you should stop using the eyelash extension.