It is the small ditch above the skin, once urine channel jammed, can produce a lot of blackhead or hoary head acne slowly, if have bacterial generation again, invade, can form the whelk that we see.

• 就是皮肤上面的小水沟，小水沟一旦堵塞了，慢慢就会产生很多的黑头粉刺或白头粉刺，假如再有细菌的产生、侵入，就会形成我们所见到的青春痘。