Hello,
From the symptoms it does not look like any skin condition because there is no rash or itching, so contact dermatitis is ruled out. You cannot lose hair of eyelashes so fast and in one or two days.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Your eyelashes don't grow in a continuous cycle as much as the rest of our hair does and tends to have a 6-8 week cycle where you'll lose a fair few and they will look sparser and shorter as they regrow. A switch in mascara really shouldn't make a difference but because you have recently switched it might be that you are more aware and watch for changes. Obviously keep a check on them and speak to your DR if you are worried but it sounds normal to me.