Frizzy hair is often due to heredity. This includes not only direct parents, but also grandparents who inherit it from other generations. If both parents have frizzy hair, their children are likely to have frizzy hair as well.
Frizzy hair due to changes in hair texture caused by age or other factors
Around the age of 40, aging causes the muscle fibers in the scalp to relax and the pores become oval-shaped, which can cause frizzy hair to appear. Even for those who say, “I didn’t have such frizzy hair when I was younger…,” it is not uncommon for frizzy hair to appear due to sebum production and the amount of moisture in the hair.