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These spiny spheres are plant pollen, as seen under a microscope.
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They're the culprit behind most seasonal allergies.
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Pollen can cause your immune system to kick into overdrive because your body sees the pollen as a harmful intruder.
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As a result, the body produces histamines.
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Normally, they promote healing by increasing blood flow and inflammation.
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But they can lead to the nasty symptoms we associate with allergies — like sneezing, runny noses, and watery eyes.
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Generally, people who suffer from allergies have it bad for several weeks during certain plants' growing seasons.
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But because of climate change, the level of pollen in the air is getting much worse.
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And that's bad news — whether you suffer from allergies or not.
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In order to grow and produce pollen, plants need to generate energy through photosynthesis.
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That requires water, sunlight, and a third necessary ingredient, carbon dioxide.
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Carbon dioxide exists naturally in the atmosphere.
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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.
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The more carbon dioxide there is in the air, the more plants grow and produce pollen.
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Take a look at this graph.
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These bars are the level of carbon dioxide in the atmosphere between 1996 and 2015.
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And this line is the amount of pollen produced per ragweed plant, a common source of allergens.
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As carbon dioxide increased, the ragweed produced more and more pollen.
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And pollen is an important part of a plant's reproductive cycle.
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So more pollen means more seeds, which means more plants producing more pollen the following season.
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But CO2 is increasing the level of pollen in another way as well.
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Carbon dioxide is a greenhouse gas.
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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.
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As the climate warms, there are more days above freezing, which means more time that plants are active and producing pollen.
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This graph shows the number of days with above-freezing temperatures in the US over the past 120 years.
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In the past 50 years, the US growing season has increased by over 10 days, on average.
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And this isn't happening at the same rate everywhere.
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This map shows the increase in pollen season for ragweed between 1995 and 2015.
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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.
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And this isn't just happening in North America.
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Overall, most places around the world are seeing longer growing seasons — and, as a result, more days with pollen as well.
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Pollen levels and allergies are only going to get worse from here if carbon emissions continue the way they are.
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This is the current production level of grass pollen, another common allergen source.
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By 2060, that level is expected to double.
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And by 2085, that amount will have more than tripled.
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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.
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But in some, allergies can lead to severe reactions like anaphylaxis, where blood pressure drops and airways start swelling shut.
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And pollen grains can wreak havoc on people's lungs, even if they don't suffer from seasonal allergies.
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In the US, asthma attacks induced by pollen have led to more than 20,000 emergency room visits per year.
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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.
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It can help curb how much we're warming the planet and it can help slow the pollen apocalypse.
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If your best strategy to avoid seasonal allergies is to stay indoors all spring,
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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.
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Hover makes it simple to buy interesting domains with great extensions like .earth or .space.
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Even if you don't need your own domain, you could set up a costumed e-mail address like "[email protected]"
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And right now you can get 10% off of your first purchase by going to Hover.com/vox.
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Hover doesn't impact our editorial, but their support makes videos like these possible.
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