Table of Contents: Benefits of Overnight Hair Masks; Are Overnight Hair Masks Safe?; Ingredients Not Suitable for Overnight Masks; Beneficial Overnight Hair Masks; How to Use Overnight Masks; How Often to Use Them. Many factors, such as pollution, chemical hair treatments, or stress, can cause your hair to become dry, brittle, and lifeless. A hair mask can help restore your hair's natural shine and vitality.