Coconut oil Trusted Source contains fatty acids that penetrate inside the hair shaft and reduce protein loss from hair. Coconut oil can be used either before or after you wash your hair depending on your hair type. If your hair tends to be oily, you can do a leave-in treatment overnight or for a few hours before you wash it. Massage coconut oil into your scalp and all of your hair. If your hair is dry, you can also use it as a leave-in treatment. There needs to be more research on coconut oil as a promoter of hair growth, but it’s been shown to improve the health and luster of hairand has been used for centuries.