It depends, if the quality of the mascara is bad, it must lead to fall of eyelashes.
The mascara is made of chemical, so there are some effect to the natural eyelashes.
Qualified mascara never make the eyelashes fall, on the contrary, they help the eyelashes to be more healthy and beautiful.
Eyelashes are located in the most important place in our body after all.
And lack of eyelashes may cause lots of eyes problems, for example, our eyes will easily get infection without the protection of eyelashes.
Yes, it is possible to get your eyelashes fallen off if you use mascara. But this is depend on the quantity you use, do not use to much or your eyelashes can not bear the irritation of mascara. Even you may loose some of your eyelashes, the new will come out several weeks later and you can not be bald of eyelashes from wearing mascara.
Ok, from what you said, I can see that you are afraid of getting fallen eyelashes out of using mascara, as a matter of fact, it is true too much mascara could give rise to fallen eyelashes, because your eyelashes are quite fragile which could be falling with overuse of mascara, since mascara could be attached to those eyelashes. And too much mascara could lead to other eye problems, such as red eyes. So try to be careful will you?