Ah, spring.
啊！春天。
Grass growing, flowers blooming, trees growing new leaves,
绿草滋生，百花齐放，树长新叶。
but if you get allergies, this explosion of new life probably inspires more dread than joy.
但如果你患了过敏症，对这些新生命的激增可能产生的恐惧多于欢乐。
Step outside, and within minutes, you're sneezing and congested.
走出户外，只消几分钟你就打喷嚏及鼻塞。
Your nose is running, your eyes are swollen and watery, your throat is itchy.
流鼻水，眼睛肿胀且泪汪汪，喉咙发痒。
For you and millions of others, it's seasonal allergy time.
对你及数百万的其他人而言，过敏症的季节到了。
So what's behind this onslaught of mucus?
这种突如其来大量黏液的原因是什么呢？
The answer lies within you.
答案就在你体内。
It's your immune system.
就是你的免疫系统。
Seasonal allergies, also called hay fever, or allergic rhinitis, are a hypersensitive immune response to something that's not actually harmful.
季节性过敏 ── 也称为「花粉热」或「过敏性鼻炎」，是一种对无害物质的过敏免疫反应。
Pollen from trees and grass, and mold spores from tiny fungi find their way into your mucous membranes and your body attacks these innocuous travelers the same way it would infectious bacteria.
来自树与草的花粉，及微小霉菌孢子进入你的粘膜，你的身体攻击这些无害的过路者采取对抗细菌感染一样的方式。
The immune system has a memory.
免疫系统具有记忆。
When a foreign substance gets tagged as threatening, white blood cells produce customized antibodies that will recognize the offender the next time around.
当外来物被贴上“具威胁性”的标签，白血球会制造特定的抗体于下一次辨识这个入侵者。
They then promptly recruit the body's defense team.
如此可迅速地动员身体的防卫成员。
But sometimes, the immune system accidentally discriminates against harmless substances, like pollen.
但有时，免疫系统会无意地排斥一些无害物质，如花粉。
When it wafts in again, antibodies on the surface of white blood cells recognize it and latch on.
当它再次飘入，白血球表面的抗体会辨识出并抓住它。
This triggers the cell to release inflammatory chemicals, like histamine, which stimulate nerve cells, and cause blood vessels in the mucous membranes to swell and leak fluid.
这会诱发细胞释放发炎化学物质，如组织胺，它会刺激神经细胞，并造成粘膜的血管肿胀及渗出液体。
In other words, itchiness, sneezing, congestion, and a runny nose.
也就是发痒、打喷嚏、 鼻塞和流鼻水。
Allergies usually, but not always, show up for the first time during childhood.
过敏症通常（但并非总是） 第一次是出现在孩童时期。
But why do some people get allergies and others don't?
但为何有些人会过敏， 而其他人不会呢？
Allergies tend to run in families, so genetics may be one culprit.
过敏症大都有家族的倾向，所以基因可能是一个起因。
In fact, errors in a gene that helps regulate the immune system are associated with higher rates of allergies.
事实上，协助调节免疫系统的基因发生错误与过敏症的较高发生率有关。
The environment you grow up in matters, too.
你成长的环境也有关。
Being exposed to an allergen as a baby makes you less likely to actually develop an allergy to it.
当婴儿时期暴露于某一过敏原时，让你较不会对它产生过敏。
People who grow up on farms, in big families, and in the developing world also tend to have fewer allergies, although there are plenty of exceptions, partly thanks to genetics.
生长在农场、大家族，及开发中国家的人也较少有过敏症，虽然有许多例外，一部分是由于遗传。
One theory is that as children, they encounter more of the microbes and parasites that co-evolved with traditional hunter-gatherer societies.
有一理论是说当孩童时，他们接触较多微生物与寄生虫，它们是与传统捕猎社会共同演化的。
Called the hygiene hypothesis, the idea is that when the immune system isn't exposed to the familiar cast of microbes, it'll keep itself busy mounting defenses against harmless substances, like pollen.
这想法称为「衍生假说」 ，也就是当免疫系统，没有暴露于常见的微生物种类下，它反而会忙于对无害物质建立防卫机制，如花粉。
Another theory is that an immune system toughened up by a barrage of pathogens is less likely to overreact to allergens.
另一个理论是受病原体猛攻后所强化的免疫系统对过敏原较不会过度反应。
Pollen is a common offender, just because we encounter so much of it, but there's a long list of substances: dust, animal dander, insect venom, medications, certain foods, that can send your immune system into overdrive.
花粉是一种常见的肇事者，只是因为我们经常接触它，但有许多的物质：灰尘、动物皮毛、昆虫毒素、药物、某些食物，能让你的免疫系统忙个不停。
Some of these reactions can be scary.
这其中一些反应会非常吓人。 每听
An allergy can develop into full-blown anaphylaxis, which typically brings on severe swelling, shortness of breath, and very low blood pressure.
过敏能演变成全身性过敏性反应，通常引起严重的肿胀，呼吸困难，及非常低的血压。 [eusoft]
It can be deadly.
它可能会致命。
The body can even have an allergic reaction to itself causing auto-immune disorders, like multiple sclerosis, lupus, and type 1 diabetes.
身体甚至可能对自己产生过敏反应导致「自体免疫性疾病」，如多发性硬化症、 红斑性狼疮及第一型糖尿病。
But even non-life threatening allergy symptoms can make you miserable, so what can you do about it?
但即使无生命威胁的过敏症状也会使你难过至极，那你该如何处理呢？
Medications can help reduce the symptoms.
药物能帮助缓解症状。
The most common ones keep histamines from binding to your cells.
最常用的药是避免组织胺与细胞结合。
These antihistamines stop the inflammation response.
这些抗组织胺药物可抑制发炎反应。
Steroids can help dial down the immune system.
类固醇能帮助减低免疫系统反应。
Another more permanent option is immunotherapy.
另一种较持久的方法是「免疫疗法」。
Deliberate, controlled exposure to gradually increasing amounts of an allergen can teach the immune system that it isn't dangerous after all.
审慎且可掌握地暴露在一种过敏原，且逐渐增加剂量，能毫无危险地教导免疫系统。
And if you're really adventurous, there's a less traditional option: intestinal parasites.
假如你真的爱冒险，有一个非正统的方法：肠道寄生虫。
When hookworms sink their teeth into the intestinal wall, they secrete chemicals that blunt the immune system.
当钩虫将牙齿插入肠壁，会分泌化学物质，减弱免疫系统。
Some studies suggest that hookworms can treat allergies, which may be another reason allergies are more common in industrialized countries where hookworms are few and far between.
有些研究指出钩虫能治疗过敏，这可能是过敏症常见於工业化国家的另一原因，钩虫在那儿是稀少而罕见的。
Of course, you can always just wait your seasonal allergies out.
当然，你可以等待季节性过敏结束。
The spring pollen onslaught dwindles by mid-summer, just in time for ragweed season.
仲夏前，春天花粉的激增会逐渐减少，刚刚好进入秋天豚草的季节 （也会导致过敏性鼻炎）
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