Sweat and Dirt
Sweat is probably one of the reasons why we need to wash our hair. After a workout or physical exercise, sweat may spread oil and make the hair feel or look very dirty. In addition, it would lead to annoying smells. Depending on your physical activities, you should shampoo your hair after wearing a helmet or hair for an extended period of time or after a workout. The same holds true when pollens, dusts, or dirts are trapped on your hair, which would make it look dull and worsen allergies. Certain styling products may accumulate on the scalp and hair, thus resulting in damage and irritation. So, if you use chemical products regularly, you also need to wash your hair more frequently. [5]
