Unfortunately, I have to say that it may be because of the eyelash extension you have used, causing eye irritation. Generally speaking, by using eyelash extension for a long time, it can lead to some serious eye diseases, such as the eye infection. And then it can make your eyes feel irritated, and red, even bloodshot. As we know that eyelashes extensions are placed directly to the natural eyelash with a bonding agent. In this way, they can carry some bacteria and also be the irritants. Finally, it can lead to eye irritation, causing red eyes. Maybe pink eyes and dry eyes will occur too. So if you do have this symptom, just give up using the eyelash extension. And some eye drops will be helpful.
Without detailed check, we can't tell whether it is really caused by eyelash extension. Yet we have to say that there is a possibility that this eyelash extension may cause such symptoms. Because eyes are very subtle. Anything get into eyes will trigger unpleasant feelings at once. Even your own eyelash getting into eyes can make your eyes grittiness feelings, not to mention the extension. According to my knowledge, eyelash extension, no matter what kind of material you chose (human hair, mink, synthetic or silk), it needs some kind of adhensive subtance to make it. And it damages your own eyelash or eyes, to some extent. Eyes are irritated easily. Or maybe your eyes are allergic to the material or adhensive staff. I suggest you to see an oculist to make sure what happened in case more damages caused.