Juniper and cedar pollen allergy

What it is

Junipers, genus Juniperus, belong to the cypress family, Cupressaceae. About 50 juniper species grow worldwide, and 13 are native to the United States.⁸ Several of them are called cedars. Ashe juniper, Juniperus ashei, also goes by mountain cedar, rock cedar, post cedar and Texas cedar.⁶ Eastern redcedar, Juniperus virginiana, is also known as red cedar or aromatic cedar.⁷

Junipers usually carry male and female cones on separate trees, though one-seed juniper and some western junipers occasionally carry both.⁸ The Texas A&M Forest Service notes that only male juniper trees release pollen, while female trees carry berry-like cones, and that the pollen can blow for miles.²

A study in PLOS ONE calls mountain cedar pollen highly allergenic and the major cause of hay fever in Texas. Its authors note that researchers consider mountain cedar the most allergenic member of the cypress family in North America.³ It causes seasonal allergic disease across broad areas of the south-central US and northern Mexico.⁴

Symptoms it causes

Mountain cedar and juniper pollen cause the winter allergy known as cedar fever. It is an allergic reaction that causes hay fever, also called allergic rhinitis. Despite the name, it is not a contagious illness or a virus.¹

Like other tree pollen allergies, it can cause a runny or stuffy nose, postnasal drip, sneezing, an itchy nose, eyes, ears and mouth, and red, watery or swollen eyes. Some people also cough, wheeze or feel short of breath. If you have asthma and are allergic to tree pollen, the pollen can trigger your asthma symptoms.¹

Where and when it grows

Mountain cedar grows mainly in central Texas. The largest stands are on the limestone slopes of the Edwards Plateau.³ Smaller, separate populations grow in southwestern Missouri and Arkansas, in the Arbuckle Mountains of southern Oklahoma, and in Coahuila, Mexico.⁶

Its timing is unusual. Mountain cedar releases pollen in winter, from early December to early February.³ Cold weather triggers it: in Texas, the trees tend to release pollen right after a cold front, when the air dries out and the wind picks up.² AAFA says cedar fever is most common from December through February in Arizona, Missouri, New Mexico, Oklahoma and Texas.¹ The pollen can travel far. Genetic testing confirmed mountain cedar pollen in winter air samples from London, Ontario, and air-flow modeling traced its path back to Texas and Oklahoma.³

Most other junipers flower later. The Fire Effects Information System says eastern redcedar, native to the eastern United States and Canada from Nova Scotia to eastern Texas, pollinates from February in the South and East to May in the North and West.⁷ The Texas A&M Forest Service notes that in more eastern parts of the state, eastern redcedars pollinate around the same time as mountain cedar, between December and January.²

In the West, alligator juniper flowers in February and March, Utah and one-seed juniper in March and April, western juniper from mid-April to mid-May, and Rocky Mountain juniper from mid-April to mid-June.⁸ University of Arizona Cooperative Extension lists both juniper and cypress among the trees that can cause pollen allergies.⁹ AAFA lists juniper in every state except Alaska and Hawaii.¹

Cross-reactions

Several members of the cypress family share very similar major allergens. The main allergen of Arizona cypress closely matches those of mountain cedar, Japanese cypress and Japanese cedar, which explains why these conifer pollens cross-react.⁵ The family as a whole is a recognized source of winter respiratory allergies.⁵ Related species in the cedar family cause similar problems around the world.⁴