* Hair type: Fine hair tends to get oily faster than thick or coarse hair.
* Scalp type: Some people have oilier scalps than others.
* Lifestyle: Frequent exercise or exposure to pollutants can necessitate more frequent washing.
* Products used: Certain styling products can build up and make hair look greasy.
* Personal preference: Some people simply prefer the feel of freshly washed hair, while others prefer the way their hair looks and feels a day or two after washing.
Some might wash daily, while others might only wash a couple of times a week.
Ultimately, the best approach is to wash your hair when it starts to look or feel oily or dirty.