In ancient times, there were doctors who were good at studying the nature of herbs. One day, the doctor was in the pharmacy, thinking about Aha, Bha and Glycolic Acid. Aha is strong in nature and can peel off the old quality of the skin; Bha is good in seepage and can pass through the stagnation of pores; Glycolic Acid is mild, and has the ability to rejuvenate while moisturizing the muscles.

The doctor wants to know if these three can be mixed into medicine to increase its effect. Then take an appropriate amount of all medicines, put them in a porcelain bowl, and carefully reconcile them. At first, the three blends smoothly, and no abnormality is found. Then let stand for a while, the color of the medicine gradually changes, and there is a slight precipitation.

The doctor looked at it, and worried that its nature would change and be harmful. So he searched all the classics and interviewed all the same people. An old man said: "The mixing of medicines is like the intercourse of people, and its nature must be carefully examined. Although each of these three has its own merits, Aha and Bha are fierce, although Glycolic Acid are mixed together, they are mixed together, and they may hurt the body due to excessive force, or the softness of the skin may cause redness, swelling and tingling."

The doctor heard it and took it for granted. Since then, when it comes to mixing medicines, he has become more and more cautious, and he must carefully observe the physical properties before he dares to act.