This is perfectly natural for a few lashes to fall out but remember to be gentle when you remove your mascara. Never wipe or pull at the lashes. It is also a good idea to pay attention to how much mascara you use. The more you use, the harder it is to remove and the wear and tear on delicate lashes can cause them to fall out.
Additional tips to avoid eyelash lost: Avoid waterproof mascara as they are the hardest to remove. Link...
