What is an important consideration when choosing the thickness of an eyelash extension?

Choosing the thickness of an eyelash extension is crucial because it directly relates to the strength of the client's natural lashes. If a client has fine or weak natural lashes, using very thick extensions could cause damage or stress to the natural lash, leading to breakage or premature loss. On the other hand, if the client has strong and healthy lashes, they can support thicker extensions without harm. Therefore, assessing the condition and strength of the client's natural lashes ensures that the extensions applied will not compromise their integrity, allowing for a beautiful and lasting result without harm.

Other considerations may be relevant, such as the length of the natural lashes, which affects how the extension appears, but it is the strength of the natural lashes that ultimately dictates a safe and effective choice in thickness.