There is no scientific evidence to prove that Vaseline helps eyelashes grow. Like every other hair on the human body, eyelashes maintain a specific growth cycle in which they grow to a certain length and then stop. Eyelashes will regularly fall out, and the regrowth time is between 4 to 8 weeks, but there is no evidence to support the assertion that cosmetic products can help lashes grow longer. The length of an eyelash is dependent on genetics and hair health and type.
Due to the thickness of Vaseline, its application will certainly cause lashes to look fuller and thicker. Like mascara, it will enhance the look of lashes, but will not cause them to grow.
People with certain hair types often complain of hair that is brittle and weak. These traits can apply to eyelashes as well. If you have lashes that fall out regularly or are susceptible to breakage, Vaseline may aid in strengthening the lashes and making the hair healthier.