Which component is essential in preventing top and bottom lashes from sticking together?

Using pacing under eye pads is essential in preventing the top and bottom lashes from sticking together during the application of eyelash extensions. The under eye pads serve as a barrier that separates the natural lashes on the upper lid from the ones on the lower lid. This separation is crucial for ensuring that the adhesive used does not accidentally bond the two sets of lashes together, which could lead to discomfort and possible damage to the natural lashes.

The under eye pads should be applied properly to cover the lower lashes, keeping them safe and ensuring that the focus remains solely on the upper lashes during the extension application process. This technique not only aids in achieving a clean and professional result but also enhances the client's comfort during the treatment.

Other options like waterproof adhesive, adjusting extension length, and applying oil-based removers, while relevant in different contexts of lash application and removal, do not specifically address the issue of lashes sticking together during the application process. Thus, they do not contribute directly to achieving the desired separation between the top and bottom lashes.