Why is my eyelash serum causing irritation now after using it for 5 months?

I have the Lash Australia eye serum, it has little ingredients that are said to be natural, so I purchased that rather than some that have ingredients 20 letters long. For the past few weeks my lash line has been very red and itchy. The ends of the eyes are the same. If I rub it too hard the redness increases. Some mornings the irritated area becomes flaky and dry. Why is this? I’ve been using this serum since the beginning of this year and I’ve never had any issues until now. It has made my lashes grow significantly so I will be sooo upset if I have to discontinue using it. Has this happened to anyone else? Are there natural alternatives to increase my lash growth? I heard castor oil helps but I’m not too sure.
Why is my eyelash serum causing irritation now after using it for 5 months?
Post Opinion