Why do new hairs fall out when you stop using hairsprays (like Minoxidil)?

This is called the “Rebound Effect.” Topical medications like minoxidil artificially nourish the hair by dilating blood vessels. The hair follicle becomes accustomed to this external support. When the medication is suddenly stopped, the hair follicle cannot find the nutrients it is used to and goes into shock, quickly entering a resting phase. Therefore, these types of treatments should be gradually reduced under medical supervision or discontinued in conjunction with treatments that strengthen the hair follicle, such as mesotherapy.