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While some people are allergic to food or pets, when we say “allergies” it’s most often referring to the snuffling, itching, and sneezing triggered by exposure to plant pollen. The springtime might bring vivid flowers, green leaves, and growing shoots, but that comes along with pollen that makes many of us miserable for months on end.

There are specific times and cues that plants look for before they fill the air with pollen so they have the best chance of success. Plants are not out to make us uncomfortable, they need to fill the air with pollen to reproduce with their neighbors. Let’s take a look at some of the ways that plants spread their pollen and how we can use that information to help allergy attacks.

What kind of pollen causes seasonal allergies?

Plants can be loosely typed into groups that release pollen at different times due to their unique strategy to make the most of sunny months. Only about 12% of plants spread pollen in the wind, but that’s plenty to make us sneeze and itch. The three most common types of pollen allergies are tree, grass, and weed pollen allergies.

Woman sneezing near a tree

Trees and colorful flowering plants, also known as angiosperms, are the most complex plants and sometimes very large, and they start very early, usually in the spring. About 80% of these plants have been relying on animals to move their pollen around since the time of the dinosaurs. However, during the interceding millions of years as useful animals were more or less available, angiosperms have also changed their shapes to spread and collect pollen in the wind.

There are dozens of conifer trees that spread allergy triggering pollen in the wind in the early spring, including cedar, juniper, birch, pine, and cypress. Conifers get their names from the pointy pollen-covered cones they poke out into the breeze, and usually have needles instead of leaves.

Woman crouching in a field of flowers to blow her nose

Grasses spread their pollen during the summer and trigger what is commonly known as hay fever, but has the same symptoms as any other respiratory allergy. Grasses are also angiosperms, but are a less complex type called a monocotyledon, or just monocot.

Diagram showing the anatomy of monocot and dicot plants

The other angiosperms are called dicots. Monocots grow many flowers low to the ground to survive grazing by herbivores, and release a lot of pollen in the early summer.

Woman blowing her nose near a bush

Weeds are not a defined category of plants, but small and low angiosperms with weed in their names release their pollen in the fall. Ragweeds are the primary culprit for these late season allergies, and the many diverse species have longer life cycle compared to other plants. Its flowers don’t open until summer, and its first shoots pop up in early October, so it is spreading pollen throughout August and September.

Why are pollen allergies seasonal?

Almost all organisms that live outside the tropical zones have strategies to take advantage of the changing seasons. Everyone has a plan to gather the most during the warm, bright, or wet months when plants are growing, and conserve as much as possible during the cold, dark, dry winter months when plants are dormant. Most if not all of the seasonal differences in animal behavior like hibernation in the winter or mating in the spring is a direct result of how much plant matter is available to the food chain. Allergy season may onset in different ways depending on how far you live from the equator.

As the days get shorter, plants become dormant. Some species just drop their leaves, some stop growing, and others may die off completely leaving only seedlings to sprout in the Spring. We can keep an eye on the pollen count in our area, but that is only part of the story.

Man blowing his nose at office desk

Why are my seasonal allergies so bad with low pollen count?

When pollen counts are reported as low on a website, there are several reasons why your allergies might still be acting up. Seasonal allergies are actually very difficult to study. Acquiring a daily pollen count with the number of pollen grains per cubic meter is simple enough, but figuring out how much pollen it takes to trigger allergies is a lot harder. Here are the main reasons why pollen count and symptoms might not match

  • The pollen detector is too far away. This is the most obvious drawback to pollen counts, they are only measured at a few select sites. If you are allergic to a tree in your front yard, then the pollen count taken miles away would be unlikely to tell you when it’s releasing the most pollen.
  • Different plants might carry the same allergy trigger. Many plants in the same botanical families produce the same allergy triggers but not all of them are necessarily in the pollen count. For example, birch is a common allergy trigger, and most pollen counts include it. But the other trees in the Betulaceae family like alder, hazel, and hornbeam produce the similar allergy triggers as birch but might not be in the pollen count.
  • Being worried about the start of allergy season can trigger allergies. A few studies have picked up that allergies seem to spike in early March before the pollen count gets very high. Reading about the impending pollen season and anticipating the onset of allergies can exacerbate and even directly cause the symptoms.
  • Spending time without an allergic reaction can trigger bigger reactions later. The immune system is complex, and exposure to some allergy triggers can make the allergy worse yet exposure to others can reduce sensitivity. For people with an allergy to one plant, the sudden exposure after almost a year of nothing can trigger a larger reaction. For people with allergies to multiple plants, the first allergy triggered can prime the immune system for a bigger response to the next one.
Baby sneezing in a field of flowers

How to prepare for allergy season

Your doctor or allergist will be your best resource. Allergies are very unique and personal, so the average website isn’t going to know enough about you to help much with allergies. Only medical professionals can administer immunotherapies, which can reduce the severity of allergic reactions. They are also the only place to get the skin-prick test, which is placing tiny amounts of different allergy triggers under the skin to get an idea of what is triggering and how severely.

If you use antihistamines, it’s a good idea to start using them before allergy season because once your body starts allergic reactions they will have limited effect. Antihistamines need to get to your immune cells to block histamine before it binds, if it’s already there the antihistamine can’t remove it or kick it out.

Close-up of an antihistamine pill for allergies

With increasing carbon dioxide and climate change, pollen seasons are getting longer and longer. When the pollen starts to come around, remember that the grains are both very sticky and tend to fragment into tiny bits that are easily stirred into the air. When getting home, change clothes immediately and put your pollen-laden clothing directly in the wash or leave it by the door. Don’t bring it into your bedroom or anywhere you plan to spend long amounts of time. When outside, wear a mask and keep it clean so you don’t start the day with yesterday’s pollen on your face.

Air purifiers can also help to remove pollen from the air, which is inevitable unless you live in a biosafety cabinet. They are best used in the bedroom, where you spend the most hours breathing. Use a HEPA filter because pollen fragments can be as small as 30 nanometers or 0.03 microns. Molekule’s PECO-HEPA Tri-Power Filters destroy organic material in the air like pollen fragments and can add one more layer of pollen reduction to your toolkit.

We are always finding new ways to tell you more about what’s in your air on this blog and on our FacebookInstagram, and Twitter accounts, so please visit when you can.


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