This is easy to understand. Modern people lead busy lives, juggling work, activities, and social engagements during the day, leaving little time to relax and enjoy a comfortable hair wash at night.
Ideally, after washing your hair at night, you should allow sufficient time for it to dry completely before bed. However, sometimes life gets too hectic—you might wash your hair after 10 PM, only to feel so exhausted afterward that your eyelids feel heavy and you can barely keep them open. Consequently, you fall asleep with your hair still damp. Older generations often warn that this will lead to headaches later on. In fact, modern scientific research has revealed that there is some truth to this belief.
It's important to understand that during metabolism, the human body constantly generates heat to maintain body temperature. This heat is simultaneously conducted through the bloodstream to the body's surface, where it is continuously dissipated to the outside environment via radiation, conduction, convection, and evaporation.
Warning: Hair salons now dot urban and rural streets, serving as leisure spots where busy workers can unwind with a relaxing hair wash. However, experts caution that this trendy practice may pose health risks.
Individuals with strong physical resistance possess normal thermoregulatory functions. Through adjustment, the processes of heat production and heat dissipation remain balanced. That is, when body temperature tends to drop, heat production increases while heat dissipation decreases, keeping the body temperature around 37°C.
However, for those with weak physical resistance, the body's ability to automatically regulate temperature and maintain normal body heat is poor. Therefore, when the whole body or a specific part becomes chilled, they are prone to catching colds.