Itchy, watery eyes. Runny nose. Scratchy throat. Yellow car. Oh, the joys of pollen season in the South.

"Whenever something's blooming, you've got pollen," said Wayne McLaurin, a University of Georgia horticulturist. Right now, he said, oak, pine and birch are the main culprits.

"Pollen's not all bad," McLaurin said. "If we didn't have pollen, we wouldn't have any flowers."

Not only is pollen a flower maker and allergy stimulator. It's also a biological marker.

"Archeologists can tell if a desert was once a forest by the presence of pollen," McLaurin said. So don't look for pollen to suddenly disappear. And frankly, it's the pollen you don't see that's the problem.

"People think goldenrod in the fall gives them allergy problems, because they see it blooming," he said. "But it's really the ragweed blooms they don't see that cause the problem."

The same can be said for pine pollen, the thick, yellow pollen seen now. Large, visible pine pollen rarely causes allergy problems, but oak usually does.

"We have an explosion of pollen in the spring," said Pam Griggs of the Atlanta Allergy Clinic, one of two certified pollen counters in Georgia. "Then everything will settle back down."

To measure the pollen in the air, the clinic uses a special sampler that raises a silicone-greased rod into the air. After 24 hours, the rod is removed and examined under a microscope to get the pollen count.

In the spring, Griggs said, pollen counts of zero to 30 are considered low. Counts of 30-60 are moderate, 60-120 high and anything over 120 extremely high.

The count on March 31 was more than 1,500.

That kind of pollen doesn't just invade your eyes and nose. It invades your house, too.

"This is certainly no time to air out your house," said Dale Dorman, a University of Georgia Extension Service housing specialist. "Keep your house closed, and turn on the air conditioner for ventilation."

But just keeping the doors and windows closed may not be enough.

"There's really no effective way to keep pollen out of a house," Dorman said. "You just have to take steps to reduce it."

Humidity affects the amount of pollen finding its way inside.

"When the relative humidity is low, the dry conditions make pollen float around in the air," Dorman said.

"Turning on a humidifier will help make those particulates fall out of the air and give you cleaner air inside your home."

Air filters on heating and cooling systems also can help filter out pollen.

"It's just something that we're going to have to put up with until the first of June," Dorman said.

How long the pollen season lasts depends on blooms.

"Some plants shed more pollen than others, just like some people sweat more than others," McLaurin said.

"Trees cause the most pollen," he said. "They shed pollen, and it falls down and we see it. Petunias shed pollen, too, but we never see it. Some pollen grains are bigger than others. Some trees have small grains but produce a lot of them, and you see them floating down."

McLaurin predicts the pollen will lighten up after April, when the trees get through shedding.

"If we get a windy day, it blows it around. If we get a good rain, it will clear it out more," he said. "So look forward to spring showers."