And now, more bad news: It's also lasting longer, prolonging the misery of the millions of people for whom spring is a punishment, not a pleasure.
Heavy snow and rain in some parts of the country have nourished a profusion of tree pollen, while a sudden shift to warm, sunny weather has made its release more robust. The deluges and, in some places, flooding have pumped up the volume on mold. Add in the wind, and the suffering skyrockets.
Warnings about the difficult season have come from allergy specialists from New York to Atlanta, Chicago to California.
"This past week has been one of the worst ever," rasped Lynne Ritchie, 70, as she bought allergy medicine this week at a Manhattan drugstore.
Dr. Stanley Schwartz hears that from patients all the time — every year, in fact, he noted with a wry smile.
"Literally, every year is the worst year," said Schwartz, chief of allergy and rheumatology for Kaleida Health and the University at Buffalo. "Now it may actually be, but when it's there and you're feeling it, you don't remember what last year was like."
What is certain is that allergy seasons in general have been getting longer and more challenging, said Angel Waldron, spokeswoman for the Asthma and Allergy Foundation.
"We do know that climate change and warmer temperatures are allowing trees to pollinate longer than usual," she said. "Although people feel things are worse than ever before, it's actually because of the longer season. It's a longer time to endure."
Pollen counts and allergy attacks vary widely from region to region, locality to locality and day to day, and no one entity tracks the full complexity of their ups and downs across the country. But everything is ripe this year for a historic season.
It's been an exceptionally rainy spring in much of the country, with several states east of the Mississippi River setting records for the wettest April since 1895. That means luxuriously blooming trees and a similar effect on mold.
"The mold will grow under the fallen leaves from last season," Schwartz said. "So if it's very wet, it isn't just the blooming plants but it's also the mold, and many people are allergic to multiple airborne allergens."
The Asthma and Allergy Foundation lists Knoxville, Tenn.; Louisville, Ky.; Charlotte, N.C.; Jackson, Miss.; and Chattanooga, Tenn.; as its "2011 spring allergy capitals," using a scoring system that measures airborne grass, tree and weed pollen; mold spores; the number of allergy medications used per patient; and the number of allergy specialists per capita.
Four of those five cities are in states — Tennessee, Mississippi and Kentucky — that all had drenching springs and significant flooding. But the suffering isn't limited to the South.
The highest tree pollen count in three years triggered a dangerous air quality warning Friday in Chicago, where allergist Dr. Joseph Leija warned in a statement: "Itchy eyes, stuffy noses and fatigue will be common among Chicagoans with sensitive respiratory systems."
In Los Angeles, rain, a heat wave and the Santa Ana winds combined for a brutal stretch in February. To north in San Jose, pollen counts are on the rise with the start of grass season, allergist Dr. Alan Heller said Friday.
The National Allergy Bureau shows high pollen counts in the Northeast this week, including Albany and New York City, with their birch, oak and maple trees, and Oxford, Ala., where walnut, pine and willows are in bloom. The bureau is part of the American Academy of Allergy, Asthma and Immunology.
"It's been a very bad season so far. ... A lot of people suffering," said Dr. William Reisacher, director of the allergy center at New York-Presbyterian/Weill Cornell Medical Center in New York City.
"A lot of people who haven't suffered in previous years have come in for the first time in several years with symptoms," Reisacher said, noting that the Northeast's sudden change from cold, snowy winter to warm spring has worsened the situation.
Full circle round, back in the South, the Atlanta Allergy and Asthma Clinic has seen no letup since late February, when unseasonable warmth had Dr. Kevin Schaffer describing this year's pollen levels as "off the charts."
Medications used in the past may not be as effective if symptoms are worse this year, Reisacher said. Many of his patients in New York have required multiple drugs, including nasal sprays, oral antihistamines and eye drops.
Madison Sasser, a 21-year-old senior at Belmont University in Nashville, left her doctor's office with two kinds of nose spray and eye drops Thursday after already enduring an allergy-related sinus infection three weeks ago — right before final exams.
"It's been awful," she said. "My eyes have been so itchy and red, and I sneeze and cough. It's just been terrible."
In Dallas, a windy spring is helping to scatter the allergens.
"We've had heavy winds and the tree pollens were in heavy bloom, and all the wind was causing a lot of people a lot of problems," said Jill Weinger, physician's assistant at the Dallas Allergy & Asthma Center, where some patients were returning for treatment after years of absence.
In Louisville, Ky., 20-year-old Jared Casey's glazed eyes scanned the aisles of a Walgreens drugstore Thursday afternoon. He greeted the allergy season with an over-the-counter purchase of Claritin-D at the beginning of February — six weeks earlier than last year.
He switched to Zyrtec at the beginning of May, when his ears began plugging up, and said his symptoms are lasting longer than in years past.
"It's been a lot worse," he said. "My ears have stayed plugged up for two weeks."
Kristen Fennimore of New Egypt, N.J., counts herself among the than 35 million Americans plagued by seasonal allergic rhinitis — also known as hay fever, a condition characterized by sneezing, stuffiness, a runny nose and the telltale itchiness in the nose, roof of the mouth, throat, eyes or ears.
Until recently, the 28-year-old legal assistant said, she was feeling pretty good and thought she might get off easy this year. But pride goes before a fall.
"I was going around bragging how my allergies weren't bad this year," she said. "Then this week, it's been horrible."