Metabolism exists everywhere in human body, therefore, old eyelashes will fall off from time to time just as our hair on the head and anywhere else of our body does, then new eyelashes and hair will grow soon again. But if your eyeslashes fall off a lot frequently, then there may be several reasons as follows. First, if your eyelashes usually fall off and easily touch your eyes, then it may be trichiasis which can be caused by overuse of eyes, untidy use of eyes, unhealthy diet and so on. If so, you should pay attention to eye hygiene work, and allowing eyes to have adequate rest, and put vegetables and fruits into your daily diet especially eat more nuts. As well you can use vitamin E and olive oil to spread on your eyelashes to add nutritions to them in case of their falling off. And if your eyelashes fall off a lot and there is increase of endocrine in your eyes, then it may be blepharitis ciliaris which refers to subacute chronic inflammation of eyelid's surface, eyelashes follicle and glandular tissue caused by eye fatigue, malnutrition and inferior makeup. You should use physiological saline to clean your eyes and then spread antibiotic oculentum on your eyelids. At the same time, you should do some exercises to enhance your immunity.