Oil
Our hair naturally produces a certain amount of oil, also known as sebum. Sebum help to hydrate the scalp and protect it from damage. However, it may also be the biggest cause of dirty hair. People with an oily head tends to have their hair clumpy and limp. The amount of oil produced may depend on certain factors, such as the weather, sex, genetics, and age. People between 20 and 30 years old tend to produce more oil than older adults and children. So, if your hair is very oily, daily washing may be a good idea. Otherwise, you may wash your hair every couple of days. [4]
