JOHN YANG: If you've been sneezing and sniffling more than ever this year you're not alone, allergy season started earlier has been more intense all over the country, especially in the north and southeast.

Ali Rogen looks at why it's so early and so bad and what people can do to ease their symptoms.

ALI ROGIN: You don't need to be a doctor or a scientist to know that this allergy season feels particularly pernicious.

All you have to do is step outside.

Every single region of the country is experiencing growth in pollen production with the Pacific Northwest expected to see the largest increase nationally over the coming decades.

To discuss the science behind allergy season and some of the medical remedies available, I'm joined by Theresa Crimmins, she's the Director for the National phonology Network, which tracks and studies seasonal biological events.

And Dr. Stanley Fineman, an allergist and the Editor-in-Chief of the Publication Allergy Watch.

Thank you so much for joining us both.

Theresa, let's start with you.

What sort of biological activity does your group track in order to draw conclusions about how humans are experiencing allergies?

And what are you seeing this year?

THERESA CRIMMINS, Director, National Phonology Network: So at the National Phenology Network, we keep track actually of seasonal events that occur in plants and animals across the country and over the whole duration of the year.

This particular spring, we have seen really early activity in plants all across the eastern U.S. And that's basically because we've had a very mild winter, followed by a whole lot of warmth early in the year.

And plants respond by leafing out and then starting to bloom in response to that warmth.

And once the plants start flowering, they start releasing pollen.

ALI ROGIN: And Dr. Fineman, what sort of symptoms are you seeing these days in your patients?

And are they worse than what you've seen before?

DR. STANLEY FINEMAN, Edito in Chief, Allergy Watch: Yeah, so the typical symptoms you see in a pollen allergy patient includes nasal congestion, itchy nose, sneezing, itchy eyes, and we seen it start earlier this year, as well, because of the higher, higher pollen counts.

Patients are now having more symptoms.

So they might have been able to tolerate it in the past.

But because it's become earlier, and it's lasting longer, there's a phenomena that's called the priming effect, where somebody may have some symptoms early in the season.

And then when it comes, the pollen raises again, they get even stronger symptoms.

So they're even worse symptoms.

So we're seeing a number of patients because of that.

ALI ROGIN: And when we talk about, Theresa, it being warmer earlier in the year, a lot of people's minds go to that's climate change.

So is there a link between climate change human manmade pollution and what you've been tracking when it comes to allergies?

THERESA CRIMMINS: Yeah, there is really.

And it traces back to the biology that we learned in in high school plants, the carbon dioxide in order to photosynthesize, and we are putting a lot more carbon dioxide in the air.

We have been for 150 years now.

And as those CO2 levels have increased in the atmosphere, we're giving plants the ingredients that they need to grow more robustly and to grow more pollen.

And so what we've seen in just recent decades, is a real clear lengthening of the growing season.

And we're projecting that the seasons will continue to get longer and the amount of pollen in the air will right now it looks like it'll continue to increase to.

ALI ROGIN: And sticking with you, Theresa, if you look at the list of where it's worse to live, when you have allergies, it's an interesting list.

The top three, Wichita, Kansas, Dallas, Texas and Scranton, PA, what lend city high on that list?

THERESA CRIMMINS: It has to do with the plants that are the most abundant on the landscape, and whether they happen to be wind pollinated.

And specifically, one of the things that's been brought up recently is the abundance of male plants versus female plants.

The pollen is generated by male plants, it's effectively sperm.

And if we have more male plants being planted on the landscape, we might expect to have more pollen in the air.

And back in the 1950s, there was a push toward planting more male trees in urban areas, because female trees are the ones that are responsible for generating fruit and fruits can be messy and create messes that have to be cleaned up.

And some of those cities seem to have a preponderance of male plants that are generating more pollen than would naturally occur.

ALI ROGIN: And Dr. Fineman, back to you.

Do you think planters need to be paying more attention to the types of plants that are going into urban areas?

DR. STANLEY FINEMAN: Years ago in the New York City area, they tried to eradicate ragweed, but of course it didn't work, especially microscopic pollen could travel 50 miles I mean, it can travel very, very far.

So even if you don't have an oak tree in your yard, your neighbor may have one and you could be allergic to it.

ALI ROGIN: How can people be managing their symptoms more effectively when allergies are really bad?

DR. STANLEY FINEMAN: They really should see an allergist to get allergy tests to find out exactly what's triggering their symptoms because once you know exactly what's triggering, you can monitor it, you know, you can follow it on a regular basis of what's in the air.

Usually when they do the allergy skin test, then you get an allergy management plan from the allergist.

And that can involve medications that could even involve allergy immunotherapy, which is allergy shots, or sublingual drops to help desensitize the patient, so they no longer have as much of a dramatic symptom effect when they're exposed to that high pollen count.

THERESA CRIMMINS: I'd love to follow up on what Dr. Fineman said.

If you can identify what your sensitivity is, then you can track what is in the air and when it is.

And my network, that's what we do.

And we run a program that invites folks of all ages and backgrounds to track exactly what they're seeing happening seasonally.

And so that program, Nature's Notebook is a perfect opportunity for tracking when different plants are in flower in your area.

And you can directly then impact your own health in that way.

ALI ROGIN: A last question to both of you, what if anything can be done to reverse this trend of allergy seasons seemingly getting longer and more intense every year?

THERESA CRIMMINS: If we can curb emissions, that would definitely slow down the rate of increase of carbon dioxide in the air and thereby kind of bend that curve in terms of the CO2 that we're feeding to the plants that is enabling them to continue to grow larger and more robustly and generating more pollen.

DR. STANLEY FINEMAN: We know that patients who are exposed to higher auto emission rates and have allergies have more severe symptoms.

So those children who live near highways have usually more severe symptoms of their asthma and of whatever allergy problem that they have, usually respiratory.

ALI ROGIN: Theresa Crimmins with the National Phonology Network, and Dr. Stanley Fineman, an allergist and the Editor in Chief of Allergy Watch, thank you so much for your time.

THERESA CRIMMINS: Thank you.

DR. STANLEY FINEMAN: Thank you.