How much saliva is secreted is evidence of youth.
Babies often wear bibs to catch water, because babies always drool a lot. Without bibs, they will get dirty immediately. Saliva contains human growth hormone. When you see your baby's saliva, you can know how much growth hormone the body secretes. But saliva will decrease with the growth of children, which means that the human body is gradually aging.
Babies grow every day, every hour, every minute and every second, and it is the growth hormone in saliva that makes them grow. Growth hormone is responsible for 15% metabolism, making bones grow, muscles strong and skin firm.
However, the amount of saliva will gradually decrease with growth, which will reduce the water in the body. Newborn skin is 90% water, so the skin is smooth and tender, but the water content of adult skin is only 68%, while that of the elderly is only 40%.