You should generally use an eyelash curler before applying mascara. There are several reasons for this:

- Better Curl Formation: Eyelashes are more malleable when they are clean and free of product. Using the curler before mascara allows you to shape the lashes more effectively, creating a more natural and long-lasting curl. If you try to curl your lashes after applying mascara, the mascara can make the lashes stiff, and it will be more difficult to achieve a smooth, even curl. The curler may also pull on the lashes, causing them to break or clump together.
- Reduced Risk of Damage: Mascara can make lashes more brittle, especially after it has dried. Curl the lashes before applying mascara helps to minimize the risk of damaging them. Curlers gripping onto mascara-coated lashes might lead to more lash breakage and fallout compared to curling clean lashes.
- Enhanced Mascara Application: Curl your lashes first creates a better base for mascara application. Mascara will adhere more evenly to curled lashes, and you'll be able to coat each lash more thoroughly, resulting in a more voluminous and defined look.
However, in some cases, such as when you want to touch up the curl after the mascara has dried or if you have very straight lashes that need an extra boost, you can use a lash curler gently over the mascara-coated lashes. But be extremely careful to avoid getting mascara on the curler pad and causing clumps or damage to the lashes.