Which material is most commonly used for eyelash extensions?

The most commonly used material for eyelash extensions is synthetic fibers. This choice is favored in the beauty industry because synthetic fibers can be manufactured to mimic the natural appearance of eyelashes while offering various benefits such as durability and a wide array of curl types, lengths, and thicknesses.

Synthetic fibers are designed to hold their shape and curl over time, enhancing the client's aesthetic without the need for frequent replacement. They are also available in various finishes, allowing technicians to create a range of looks from natural to dramatic.

In contrast, natural hair, such as mink or sable, can be more expensive and comes with ethical considerations related to sourcing and maintaining. Silk is a specific type of synthetic fiber that is sometimes used and appreciated for its lightweight nature and sheen, but it is not as prevalent as the broader category of synthetic fibers. Cotton is not typically used for eyelash extensions, rather it's more commonly associated with products like cotton swabs or pads, which have no role in the application of the extensions themselves.

Thus, synthetic fibers stand out as the most practical choice for mass appeal and a variety of styling options in eyelash extensions.