Oil
Teenagers and 20- and 30-year-olds produce more sebum than children and older individuals. If you had an oily scalp, it can dry out with age.
Type of hair
Wash straight, thin hair more often than curly or wavy hair. Straight hair gets oily quickly because sebum coats it easily.
Sweat
Sweaty workouts can ruin your hair, as expected. How often you wash or rinse your hair depends on how much you sweat.
Physical dirt or pollen
Cleaning, gardening, and other filthy chores may require a wash. Hair can trap dirt, dust, and pollen. These might dull hair and worsen allergies.
Styling products
Styling products can irritate and damage hair and scalp. Regular or heavy product use may require more frequent hair washing than without creams and sprays.
Dandruff and shampoo
Your dandruff may be from overwashing. Overly dry scalps cause dry hair, itching, and dandruff. But that doesn't imply we should stop shampooing our hair.
Dry shampoo
The powder or spray cleaner doesn't clean your hair. Instead, it absorbs oil to avoid hair clumping.