A、Healthy skin
A healthy skin is slightly moist, soft, flexible; possesses a slightly acid reaction; and is free from any disease or disorder. The skin also has immunity responses to organisms that touch or try to enter it. Its texture (feel and appearance) is ideally smooth and fine grained.

B、The causes of injured skin
The ultra-violet rays of the sun
Air pollution
Alcohol, drugs, and tobacco
Frequent weight gain and loss suddenly
Excessive massage
Unadequate diet, insufficient sleep

C、Skin-Ageing Stage