Using green tea on eyelashes to promote growth is based on the antioxidants in green tea, especially catechins, known for promoting overall hair health. While some believe it helps, scientific evidence is limited. Green tea extracts may aid general hair growth, but more research is needed for eyelashes. But, if you decide to try it, make a green tea infusion, let it cool, and apply to lashes with a clean spoolie or Q-Tip.  Results vary, so do a patch test. Be realistic about home remedies, as scientific backing may be lacking.