“Cedar fever” season has arrived in Texas, putting millions of people at risk for colds and sniffles as Christmas approaches.

While “cedar fever” may sound like some exotic disease, it’s actually an allergic reaction to the pollen released by ash junipers, also known as mountain cedars.

These trees release huge amounts of pollen during the winter months, which can trigger allergic rhinitis or hay fever.

“Cedar fever is an irritant to many because of the abundance and density of ash junipers in Central Texas, all of which produce pollen at the same time, resulting in high concentrations of pollen in the air,” said Robert Edmonson, a biologist and certified arborist with the Texas A&M Forest Service, said in declaration.

Symptoms of cedar fever can include a runny nose, sore throat, fatigue, loss of smell, and sometimes fever.

Mountain cedar pollen is not particularly allergenic, but the sheer amount released by the trees during December and January means that airborne concentrations are very high in some areas.

“Cedar fever is worst west of I-35 where you have primarily juniper mixed with oaks and some other species,” Jonathan Motsinger, chief of Central Texas operations for the Texas A&M Forest Service, said in a 2020 statement.

“And because all those junipers are producing pollen at the same time, you get a higher concentration of pollen in the air.”

Mountain cedars begin releasing their pollen in mid-December, usually following a cold front that is then spread far and wide by windy winter weather. This pollen is usually released continuously, peaking in mid-January before slowly fading as spring approaches.

“After a cold front, the air dries out, the wind blows, and the pressure is different. Under these conditions, every single pollen cone on a juniper opens at one point and it looks like the trees are on fire.” It looks like smoke is coming out of them,” Edmonson said in 2020.

Cedar fever can also be exacerbated by pollen from eastern redcedars in East Texas, as they also pollinate during the winter, further increasing pollen concentrations in the air.

“There’s just so much pollen in the air that it absolutely overwhelms the immune system. It’s like trying to breathe in a dust storm,” Edmonson said.

Most trees release their pollen in the spring, which is when people usually expect to have hay fever, meaning that cedar fever is often mistaken for a seasonal illness like the flu or colds, which also increase during the winter months.

“If your mucus clears, then it’s an allergy,” Edmonson said. “If it’s colored, then it’s probably a cold or the flu.”

The Texas A&M Forest Service has suggested treating cedar fever with allergy medications and antihistamines. Local news can inform you of the day’s pollen concentrations, allowing you to limit your outdoor exposure on high pollen days.

Using air purifiers can help reduce indoor allergens, and keeping windows closed helps prevent pollen from entering your home or car.