癢??！
癢是一種令人抓狂且沮喪的體驗(yàn)，特別是撓破了皮膚使得情況更糟的話。
But there are certain disorders that actually result in people itching uncontrollably without relief. In one case study, a woman had such an itchy scalp she scratched through to her brain.
但是存在一些疾病使患者感到無法抑制的瘙癢。在一起病例中，一位婦女頭皮發(fā)癢難耐，最后她甚至抓傷了大腦。
Itching is an incredibly strange sensation that scientists still don't fully understand.
瘙癢是種令人難以置信的奇怪感覺，科學(xué)家還未完全地了解。
The itch sensation is technically known as pruritus, and it's thought to have evolved as a way to protect skin - our largest organ - from parasites and build-up of dead cells.
癢的感覺在技術(shù)上被稱為瘙癢癥，它被認(rèn)為是一種皮膚——我們身體中最大的器官——的保護(hù)機(jī)制，防止寄生蟲和死細(xì)胞積聚在體表。
After all, all our other organs are tucked away safely inside our bodies, where they can be fully protected by the immune system. But our skin is our first line of defence, constantly in contact with the outside world, so it makes sense it evolved some unique ways to stay intact.
畢竟，我們所有的其他器官都安全地隱藏在我們的身體內(nèi)，在那里它們可以受到免疫系統(tǒng)的完全保護(hù)。而皮膚是我們的第一道防線，時刻與外界接觸，因此它具有一些獨(dú)特的自保方式。
It also explains why itching is contagious - back in the palaeolithic days when we all lived in close quarters, if you saw an infested tribesmate scratching away at themselves, it would make sense that you should start scratching too, in order to avoid being bitten or infected by whatever was bothering them.
這也解釋了為什么瘙癢具有傳染性——回到舊石器時代，當(dāng)我們聚在洞穴中共同生活時，如果你看到某個部落里的同伴不停地搔癢，那么你也下意識地感到癢就是有意義的反應(yīng)，因?yàn)橐苍S造成同伴瘙癢的蚊蟲跳蚤也落到了你的身上。
But it doesn't explain why an itch produces such a unique and maddening sensation.
但以上觀點(diǎn)并不能解釋為什么癢這種感覺如此獨(dú)特和令人發(fā)狂。
Up until a decade ago scientists actually thought an itch was just another, milder type of pain - using the same receptors in the epidermis that relay chemical and electrical messages up the spine and to the brain to tell it something hurts.
直到十年前，科學(xué)家才真正意識到瘙癢只是另一種更輕微的疼痛感——癢和痛使用表皮中的同一套受體將化學(xué)和電子信息傳遞到脊柱和大腦，告訴身體某處感到疼痛。
But we now know that itching actually has its own specific circuitry, involving its own chemicals and cells.
但我們現(xiàn)在知道瘙癢感實(shí)際上有其獨(dú)特的電化學(xué)線路，涉及特定的化學(xué)物質(zhì)和細(xì)胞。
And while we all have different responses to pain, we share a universal response to itching.
我們對疼痛反應(yīng)不一，但對瘙癢有著共同的反應(yīng)。
Scratching.
撓。
It turns out scratching feels so good because it causes a low-level pain signal to shoot up to the brain and override the itch signal to provide us with relief. That's why pinching or slapping the itchy spot can work, too.
事實(shí)證明，用撓來搔癢，體驗(yàn)非常好，因?yàn)樗鼤?dǎo)致向大腦發(fā)送低水平的疼痛信號，并覆蓋癢信號，緩解了癢感。這就是為什么捏捏或拍打發(fā)癢的叮包也可以起作用的原因。
Unfortunately, some of those relieving chemicals, including serotonin, can actually make it easier for the itch signal to be re-triggered.That's why it's common for scratching to make you more itchy, kicking off a vicious cycle scientists call the itch-scratch cycle.
不幸的是，撓撓時釋放的解癢的化學(xué)物質(zhì)，包括血清素，實(shí)際上會使瘙癢信號更容易被重新觸發(fā)。這就是為什么抓撓讓你更癢，開始一個被科學(xué)家稱之為癢刮傷周期的惡性循環(huán)的常見原因。
Damage to the nerves involved in that cycle can result in uncontrollable itching, without any stimulus; when that happens, these are jointly known as pruritus disorders.
周期中造成的神經(jīng)的損傷可導(dǎo)致無任何外界刺激下的無法控制的瘙癢;如果出現(xiàn)了這種情況時，可以稱之為瘙癢癥。
There are loads of reasons why these occur, and sometimes researchers don't even know the cause. Some can be caused by viral infections that affect the nervous system, such as postherpetic itch, which can be triggered by shingles.
具體的病例有很多原因，有時研究人員甚至無法確定其原因。有些可能是由影響神經(jīng)系統(tǒng)的病毒感染引起的，例如帶狀皰疹引起的皰疹后瘙癢。
There are also conditions such as brachioradial pruritus, which is caused by a restricted nerve in the neck. And aquagenic pruritus, which is itching experienced after contact with water. Some cases have actually been linked to a rare condition where the body has too many red blood cells.
還存在諸如肱橈瘙癢癥的情況，其由頸部神經(jīng)系統(tǒng)不暢通所引發(fā)。還有水源性瘙癢，皮膚接觸水后發(fā)癢。有些病例實(shí)際上與身體紅細(xì)胞過多的罕見病癥有關(guān)。
All of these disorders can leave people with a frustrating itch, often without an obvious cause and potentially without relief, too.
所有這些都會讓人感到沮喪，往往沒有明顯的原因，也可能無法得到緩解。
In an extreme case study, a woman who'd suffered from shingles had such an itchy scalp that within a year she had "painlessly" scratched straight through her skull and into her brain.
在一極端的研究案例中，一位患有帶狀皰疹的女性因持續(xù)性頭皮發(fā)癢，一年之內(nèi)她就“毫無痛苦地”直接抓破頭骨劃傷了大腦。
Plus, scientists are still learning more all the time about our curious and unique itch response, so in the future we might finally be able to turn off uncontrollable itching for good.
科學(xué)家們?nèi)栽诓粩嗵剿鞲鞣N奇怪和獨(dú)特的瘙癢反應(yīng)，所以在未來某天，我們一定可以最終消除那些難以忍耐的瘙癢。
