They're the culprit behind most seasonal allergies.

它們就是造成季節性過敏的元兇。

Pollen can cause your immune system to kick into overdrive because your body sees the pollen as a harmful intruder.

花粉會讓你的免疫系統過度疲勞，因為你的身體會將花粉視為有害的入侵者。

As a result, the body produces histamines.

因此你的身體就會產生組織胺。

Normally, they promote healing by increasing blood flow and inflammation.

正常情況下，組織胺會藉由增加血流量和發炎來促進傷口復原。

But they can lead to the nasty symptoms we associate with allergies — like sneezing, runny noses, and watery eyes.

但它們也會引起跟過敏有關的討厭症狀，像是打噴嚏、流鼻涕、和流眼淚。

Generally, people who suffer from allergies have it bad for several weeks during certain plants' growing seasons.

一般來說，會過敏的人會在特定植物的生長期發作幾個禮拜。

But because of climate change, the level of pollen in the air is getting much worse.

但由於氣候變遷，空氣中出現的花粉數量就越來越多了。

And that's bad news — whether you suffer from allergies or not.

不論你會不會過敏，這都不是什麼好事。

In order to grow and produce pollen, plants need to generate energy through photosynthesis.

為了要生長並產生花粉，植物必須透過光合作用產生能量。

That requires water, sunlight, and a third necessary ingredient, carbon dioxide.

這個過程需要水、陽光，和第三個必要的元素——二氧化碳。

Carbon dioxide exists naturally in the atmosphere.

二氧化碳原本就存在於大氣層之中。

But as we burn fossil fuels like coal in power plants or gasoline in our cars, we're putting more and more CO2 into the air.

但當我們在發電廠燃燒煤炭這類的化石燃料，或是燃燒車子使用的汽油時，就會釋放出更多二氧化碳到空氣中。

The more carbon dioxide there is in the air, the more plants grow and produce pollen.

空氣中的二氧化碳越多，植物就會長得越多，所產生的花粉也會越多。

Take a look at this graph.

讓我們看看這張圖表。

These bars are the level of carbon dioxide in the atmosphere between 1996 and 2015.

這些長條是 1996 到 2015 年之間，二氧化碳在大氣中的濃度。

And this line is the amount of pollen produced per ragweed plant, a common source of allergens.

這條線則是每一株豚草所產生的花粉量，豚草的花粉是常見的過敏原。

As carbon dioxide increased, the ragweed produced more and more pollen.

隨著二氧化碳增加，豚草產生的花粉也越多。

And pollen is an important part of a plant's reproductive cycle.

花粉是植物在生殖週期中重要的一環。

So more pollen means more seeds, which means more plants producing more pollen the following season.

所以花粉越多也意味著種子越多，也就代表下一季會有更多的植物產生更多的花粉。

But CO2 is increasing the level of pollen in another way as well.

但二氧化碳同時也用另一種方式讓花粉的濃度增加。

Carbon dioxide is a greenhouse gas.

二氧化碳是溫室氣體。

And it's called that because it traps the sun's heat energy in the Earth's atmosphere and is helping warm the planet — sort of like a greenhouse.

之所以叫溫室氣體是因為它能夠將光的熱能留在地球的大氣層，讓我們的星球保持溫暖，就像溫室的功能一樣。

As the climate warms, there are more days above freezing, which means more time that plants are active and producing pollen.

當氣候越來越溫暖，一年之中就會有越多天的溫度高於攝氏零度，這就表示植物活躍、產生花粉的時間也越長。

This graph shows the number of days with above-freezing temperatures in the US over the past 120 years.

這張圖表指出美國在過去 120 年來溫度高於冰點的天數。

In the past 50 years, the US growing season has increased by over 10 days, on average.

在過去 50 年，美國的生長季平均增加了 10 天。

And this isn't happening at the same rate everywhere.

每個區域增長的速率並不相同。

This map shows the increase in pollen season for ragweed between 1995 and 2015.

這份地圖顯示在 1995 到 2015 年之間，豚草花粉散播之季節的增長。

While some places, like Texas, didn't see much change in their ragweed pollen season, most places — especially those in the northern US and southern Canada — saw pollen season increase by almost a month.

有些地方，像德州就沒太大的變化；但絕大多數的地點，尤其是美國北部和加拿大南邊的花粉季節增加了將近一個月。

And this isn't just happening in North America.

這也不是北美獨有的現象。

Overall, most places around the world are seeing longer growing seasons — and, as a result, more days with pollen as well.

整體而言，全球大多數地方的生長季都越來越長，因此花粉飄散的日子也就變多了。

Pollen levels and allergies are only going to get worse from here if carbon emissions continue the way they are.

如果碳排放量持續增長，從此以後，花粉的數量和過敏問題只會越發嚴重。

This is the current production level of grass pollen, another common allergen source.

這是草花粉現在的濃度，它是另一種常見過敏原的來源。

By 2060, that level is expected to double.

到了 2060 年，它的濃度預計會是現在的兩倍。

And by 2085, that amount will have more than tripled.

到了 2085 年 則會成長到三倍。

While allergies can be annoying for the 1 in 5 Americans that suffers from them, they can usually be kept at bay with over-the-counter drugs.

雖然五個美國人當中就有一個會受到過敏的侵擾，但藥局賣的藥大多都可以控制他們的情況。

But in some, allergies can lead to severe reactions like anaphylaxis, where blood pressure drops and airways start swelling shut.

但對有些人來說，過敏會導致非常嚴重的過敏反應，像是其引發的過敏性休克會讓血壓迅速下降、呼吸道腫脹造成呼吸困難。

And pollen grains can wreak havoc on people's lungs, even if they don't suffer from seasonal allergies.

即便有些人不會受到季節性過敏所苦，花粉粒仍會在人類的肺部肆虐。

In the US, asthma attacks induced by pollen have led to more than 20,000 emergency room visits per year.

在美國，每年都有20000 人因花粉引起的氣喘送急診。

So if for no other reason than to protect your sinuses, it's important to reduce the amount of CO2 we're adding to the atmosphere.

所以如果沒有任何方法可以保護你的鼻竇，那最重要的就是減少我們排放到大氣層的二氧化碳。

It can help curb how much we're warming the planet and it can help slow the pollen apocalypse.

這樣可以抑制我們繼續加熱地球，也能夠減緩「花粉末日」的來臨。

If your best strategy to avoid seasonal allergies is to stay indoors all spring,

如果整個春天都待在室內是你避免季節性過敏的絕佳策略，

then you might want a way to stay connected and that couldn't be easier to do from the safety of your pollen-free bunker.

如果你想要跟外界保持聯繫，最簡單的方法莫過於待在你那既安全又可以免於花粉攻擊的碉堡裡。

Hover makes it simple to buy interesting domains with great extensions like .earth or .space.

Hover 可以讓你輕鬆買到有趣的網域名稱，像是 .earth or .space.，而且還可以擴充。

Even if you don't need your own domain, you could set up a costumed e-mail address like "danush@histaminescanbiteme.net"

就算你不需要自己的網域，也可以客製自己的電子信箱，像是「[email protected]」。

And right now you can get 10% off of your first purchase by going to Hover.com/vox.

如果你是第一次在 Hover.com/vox 購買，就可以享有 9 折優惠。

Hover doesn't impact our editorial, but their support makes videos like these possible.

Hover 並沒有影響我們的編輯自主權，但是因為有他們的支持，我們才能夠製作出這些影片。