There is no substantial evidence that daily hair washing damages hair or causes dryness. A normal person's scalp contains 144–192 sebaceous glands per square centimeter, which continuously secrete oils daily. After washing, hair naturally reabsorbs oils within four hours, restoring its natural shine and elasticity.
Whether you wash your hair daily or not, using the correct method not only avoids damaging your hair but also stimulates normal sebaceous gland secretion. This maintains and regulates sebum balance, keeping your hair lustrous and resilient.
Conversely, excessive sebum can easily accumulate dirt and dandruff, clogging hair follicles and sebaceous glands. This disrupts normal sebum secretion, hinders nutrient absorption at the hair roots, and leads to dry, brittle hair. In severe cases, it may even cause hair loss. Additionally, dirty hair can become a breeding ground for harmful microorganisms, triggering folliculitis and sebaceous gland inflammation.
Of course, even without harm, daily washing isn't necessary. Frequency should vary based on season and hair type. Those with oily hair or during summer may wash daily, though shampoo isn't required every time, and minimize blow-drying. Those with normal or dry hair can adjust to washing three to four times weekly.