How Allergies WorkPart 1 in my seasonal allergies series.

by James Hubbard, MD, MPH

For some of us, the spring season is a beautiful trap. It entices us outside with such great weather but hides an unseen danger—pollen.

But truth be told, it’s not the pollen that’s the trouble. It’s the body’s reaction to it. In about 30 percent of people, the immune system goes way overboard to protect them from pollen, which their bodies see as an invader. This is called an allergic reaction.

There are medicines that can combat the miserable symptoms, but to understand which ones you might want to store, it helps to know how an allergic reaction works so you’ll know what you’re trying to combat.

What Is an Allergic Reaction?

An allergic reaction is what happens when the body’s immune system overreacts to some usually benign foreign object, such as pollen, animal dander, a food, or a medicine.

In the case of pollens, the body may react to only one type or to many. Tree, grass, and weed pollens, along with molds, are the major players here, and one or another is in the air all year long. (Ragweed tends to like the fall).

Where’s the Pollen?

Those drifting fuzzballs you sometimes see give away the fact that pollen is in the air, but they’re actually seeds. The pollen is dust size or smaller—sometime microscopic. It’s essentially plant-world sperm sent out by the billions to fertilize any female plants it can come in contact with. Unfortunately, we humans get in its way.

What Happens During an Allergic Reaction?

What we call an allergic reaction is a series of cascading events:

  1. You’re exposed to something (pollen in this case) that for some reason, your immune system doesn’t like.
  2. At the system’s command, specialized, histamine-filled “mast” blood cells burst open and spread the histamine into your blood and tissues, targeting the area where the body detects the invaders.
  3. Histamine dilates blood vessels (makes them wider) so even more mast cells, along with antibodies and other disease fighters, can get where they need to be. It also increases body secretions (giving histamine easy travel and helping remove germs) and triggers inflammation, whose purpose is to kill the invader.

This process is similar to what happens during a cold. But in an allergic reaction, there’s really no invader to kill, so all the histamine does is create nasal and sometimes bronchial swelling due to the increased blood flow; watery eyes and nose due to the increased secretions; and the itching, sneezing, and just overall feeling bad from the inflammation.

What About Rashes and Anaphylaxis?

Along with inducing other secretions, histamines can make tiny blood vessels leak, causing lumpy, swollen lesions on the skin called hives (urticaria).

In some instances histamines, with other chemicals, cause the ultra-dangerous anaphylaxis. Fortunately, anaphalaxis is extremely rare (but possible) with seasonal allergies.

What If I’ve Never Been Allergic?

You might have a repeated exposure to a potential allergen for years without a problem. Then, for some reason (we’re not sure why), after the second or maybe the hundredth exposure, your body will all of a sudden deem it an enemy. And from then on, you’re allergic. It’s true some kids may grow out of some allergies, but don’t count on it. In general, once your body doesn’t like something, it tends to not like it for life.

What Are the Best Ways to Treat Seasonal Allergies?

Take steps to avoid breathing in the pollen when you can. You may also want to try home remedies. Nasal irrigation is popular. Click here for some prevention and remedy tips.

The big two medical-treatment categories are:

  1. Medicines, many of which were previously available by prescription only and are now over the counter.
  2. Immunotherapy—a series of shots with increasing dosages of the allergen(s) you’re allergic to, with a goal to make you less allergic.

Now that you know how allergies work, you can understand why medicines called antihistamines are usually the first medicinal line of defense against them. But your pharmacy is probably chock-full of different types of antihistamines, plus decongestants and nasal steroids. And then there are the prescription meds. So next week, I’ll help you sort through all the options to help you decide which one(s) to try.

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Do you have seasonal allergies? When do they usually kick in?


Photo: Flickr/Takashi Hososhima, “World’s breathtaking beauty,” shared via CC BY-SA 2.0.