Do you use eyelash serum?

My eyelashes are sparse and on the shorter side, so even when I apply mascara, it doesn't really show.

I looked into it and found out there are eyelash serums, so I tried the product from Etude House. You just apply it to your eyelashes before bed, and the amazing thing is that the effects appeared in less than a week.

My eyelashes haven't gotten thicker, but they have gotten really long. So I apply it for a week and then stop, but if they feel a bit short, I use it for about 3-4 days. The effect is good, but I feel a bit uneasy because I think it might not be good for my eyes.

For those of you who are concerned about your eyelashes like me, do you use eyelash serums?