【英语时差8，16】痒痒

 When you have an itch¹, you scratch it. What could be more simple than that?   Scratching itches² is one of our most basic instincts, one which we share with many other animals. Have you ever stopped to wonder, mid-scratch, exactly why scratching is so effective against itching³? We'll learn the itchy truth, on today's Moment of Science.

On the most basic level, scratching is a way to remove whatever irritant might be causing the itch in the first place. If an insect is biting you, or you have a patch of dead, flaking⁴ skin, scratching has a good chance of getting rid of it. In this case, it's pretty obvious why the scratching works.

Much of the time we scratch, however, it seems to be somewhat after the fact. Perhaps the mosquito has already bitten us and flown away, and we are left scratching at the swelling⁵ bite. Clearly this won't get rid of the mosquito. Is there any good reason for this kind of scratching, or is this just an over-zealous instinct that doesn't realize it's too late?

Actually, this kind of scratching can serve two additional functions. First, it can stimulate⁶ the irritated tissues and cause extra blood to flow to them. This can help your immune system remove whatever itchy substances might be below your skin. Second, it can trick your brain into ignoring the annoying itch. Your nervous system can generally process only one stimulus⁷ from a given area of your skin at a time. If you scratch at an area that itches, this new, greater stimulus can override⁸ the itching, effectively blocking it out. 

1 itch   

n.痒，渴望，疥癣；vi.发痒，渴望

参考例句：

• Shylock has an itch for money.夏洛克渴望发财。
• He had an itch on his back.他背部发痒。

2 itches   

n.痒( itch的名词复数 )；渴望，热望v.发痒( itch的第三人称单数 )

参考例句：

• His wool shirt always itches him. 他的羊毛内衣总是使他发痒。 来自《现代汉英综合大词典》
• This wool shirt itches my back. 这件羊毛衫使我背上发痒。 来自《现代英汉综合大词典》

3 itching   

adj.贪得的，痒的，渴望的v.发痒( itch的现在分词 )

参考例句：

• The itching was almost more than he could stand. 他痒得几乎忍不住了。 来自《现代汉英综合大词典》
• My nose is itching. 我的鼻子发痒。 来自《简明英汉词典》

4 flaking   

刨成片，压成片； 盘网

参考例句：

• He received ointment for his flaking skin. 医生给他开了治疗脱皮的软膏。
• The paint was flaking off the walls. 油漆从墙上剥落下来。

5 swelling   

n.肿胀

参考例句：

• Use ice to reduce the swelling. 用冰敷消肿。
• There is a marked swelling of the lymph nodes. 淋巴结处有明显的肿块。

6 stimulate   

vt.刺激，使兴奋；激励，使…振奋

参考例句：

• Your encouragement will stimulate me to further efforts.你的鼓励会激发我进一步努力。
• Success will stimulate the people for fresh efforts.成功能鼓舞人们去作新的努力。

7 stimulus   

n.刺激，刺激物，促进因素，引起兴奋的事物

参考例句：

• Regard each failure as a stimulus to further efforts.把每次失利看成对进一步努力的激励。
• Light is a stimulus to growth in plants.光是促进植物生长的一个因素。

8 override   

vt.不顾，不理睬，否决；压倒，优先于

参考例句：

• The welfare of a child should always override the wishes of its parents.孩子的幸福安康应该永远比父母的愿望来得更重要。
• I'm applying in advance for the authority to override him.我提前申请当局对他进行否决。