Can you sleep with a hair mask in?

It is generally not recommended to sleep with a hair mask in unless the product is specifically labeled as a leave-in mask. Most hair masks are designed to be rinsed out after a short processing time. Leaving a rinse-out mask in overnight may cause the hair to feel heavy or greasy. Always follow the product instructions for the best results. If your hair needs longer-lasting care, choose a leave-in product that is specifically formulated to remain in the hair.