How do you rehydrate mascara?

To rehydrate mascara, add a few drops of a suitable liquid, such as saline solution, eye drops, or a makeup setting spray, into the tube. Close the mascara tightly and gently shake it to mix the ingredients. Avoid adding water, as it can introduce bacteria and spoil the product. If the mascara is too old or clumpy, it may be best to replace it instead of trying to rehydrate it.