Dermatologists advise that hair and scalp needs change over time due to factors like age, hormones, lifestyle, and environment. Sticking to the same shampoo for years may no longer be suitable as the scalp's condition evolves. What was once effective for oily scalps might lead to dryness or sensitivity later. Experts emphasize that shampoos maintain scalp health, which is living skin affected by various internal and external factors, necessitating adjustments in haircare routines to address issues like itching, dandruff, or hair fall.