What is mountain cedar or cedar fever?

Mountain cedar (Ashe juniper) releases its winter pollen across Central Texas, opening mid-December, cresting mid-January, and falling away by early March. The local nickname for the resulting misery is cedar fever.

Which trees are worst for allergies?

AAFA places oak, ash, hickory, pecan, walnut, willow, mulberry, and box elder at the top of the allergenic rankings, adding alder and birch as other highly relevant species.

How big is tree pollen?

Grains are tiny and built for distance: oak measures about 24 to 38 microns, birch about 20 to 23 microns, and Ashe juniper about 25 to 36 microns.

Why does eating apples make my mouth itch in spring?

Birch pollen triggers oral allergy syndrome when raw apple, almond, carrot, celery, cherry, hazelnut, kiwi, peach, pear, or plum are eaten; their proteins mirror birch pollen component Bet v 1. Heat generally neutralizes the proteins and ends the reaction.

Is tree pollen getting worse?

Overall pollen prevalence is up about 21% since 1990, with tree pollen rising faster than pollen from grasses or weeds.

Tree Pollen Allergy: Season by Region and the Worst Trees

Tree pollen opens the allergy calendar each spring, and by volume it’s the season’s primary trigger. Wind does the work for wind-pollinated oaks, birches, maples, cedar, junipers, ashes, hickories, mulberries, and box elders. AAFA confirms these quiet, pollen-laden species—not the brilliantly colored insect-pollinated ornamentals—are what set off symptoms.

The grains are lightweight and dry, so they travel far. Oak spans about 24 to 38 microns, birch fits between 20 to 23 microns, and Ashe juniper (mountain cedar) registers 25 to 36 microns. Pollen counts nationwide have tracked upward: since 1990 the total load rose about 21%, with tree pollen increasing faster than grass or weed pollen.

Wind is the only carrier that counts. Dogwoods, magnolias, and other showy, insect-pollinated trees release heavy, sticky grains that cling to petals rather than ride the breeze. Yet their eye-catching blossoms draw the blame while a nondescript oak or birch nearby quietly dumps far more allergenic dust. Recognizing the real culprits simplifies spring planning.

Tree pollen leads the allergy year

Trees (highlighted) are first out each spring — earlier in the warm South, later in the cold North.

Tree

Grass

Ragweed

Season windows are the deterministic seasonal-estimate model (see methodology); the tick marks each type’s peak month. Not measured counts.

When is tree pollen season?

Across most of the U.S., tree pollen grabs the spotlight from February through April. Southern zones may see the first grains as early as December or January. Central Texas breaks the norm: mountain cedar (Ashe juniper) pollinates during the colder months. Mid-December marks the onset, a peak lands in mid-January, and the taper arrives by early March. Locals call the reaction cedar fever, a term documented by Cleveland Clinic and Texas A&M.

The worst trees

AAFA identifies oak, ash, hickory, pecan, walnut, willow, mulberry, and box elder as leading allergy offenders and flags alder and birch as additional heavy hitters. Regionally, oak, maple, birch, juniper, and pine dominate the skies. One neighborhood oak or birch can seed the air for blocks, so local landscaping drives exposure more than whatever blooms in your own yard.

Birch and the food cross-reaction

Birch is behind a distinctive oral allergy syndrome. Raw apple, almond, carrot, celery, cherry, hazelnut, kiwi, peach, pear, and plum possess proteins modeled after birch allergen Bet v 1, according to ACAAI. The result is typically an itchy mouth or throat confined to the oral cavity. Heat unravels these proteins, so cooking the fruit or vegetable usually removes the reaction.

Managing tree-pollen season

Early arrival makes tree pollen easy to miss, especially the December–to–March cedar surge in Texas. Follow local pollen counts starting in late winter and begin medication before the heaviest stretch rather than chasing symptoms later. Shut windows on dry, blustery days; switch on the AC; and shower off hair and skin at night. If symptoms disrupt daily routines, an intranasal corticosteroid spray offers the strongest single option broadly available.

The trees that trigger the most people

Grain diameters drawn to scale — the smaller, buoyant grains travel farther and sensitize more people.

Birch20–23 µmsmall · potent

Cedar20–30 µm

Oak24–38 µm

Grain diameters in microns. Source: NIH/PMC, AAAAI National Allergy Bureau.

Tree pollen, by the numbers

+21%

more tree pollen than in 1990

Anderegg 2021, PNAS

24–38µm

oak pollen grain diameter

NIH/PMC

20–23µm

birch pollen grain diameter