Cedar fever season is upon us once again, complete with runny noses, itchy eyes and general misery. But what exactly is cedar fever and why is it so insufferable this time of year? For starters, cedar fever isn’t a flu or a virus—it is an allergic reaction to the pollen released by mountain cedar trees. In Texas, the predominant species of mountain cedar is the Ashe juniper.
The sheer quantity and density of Ashe junipers in central Texas is one of the main factors contributing to cedar fever. According to Karl Flocke, a woodland ecologist for Texas A&M Forest Service, the pollen from Ashe junipers isn’t particularly allergenic or harmful—it’s just so concentrated that even if you aren’t generally susceptible to allergies it could still affect you.
Since the pollen is spread by the wind, cedar fever can affect individuals far removed from areas with a high concentration of juniper trees. And the source isn’t limited to Ashe junipers. In more eastern parts of the state, there are also eastern red cedars that pollinate around the same time and can induce a similar response from people’s auto-immune systems. Besides the sheer quantity of pollen released, cedar fever is mostly problematic because of when the pollen is released. Most trees pollinate in the spring when many are expecting to have allergic reactions. While ragweed pollen and mold spores can contribute to allergies in the fall, very few plants pollinate during the winter. Juniper trees are the exception.
“Immediately before and after a cold front, it gets very dry and windy and the pressure changes very rapidly,” said Flocke. “This triggers the opening of pollen cones and the release of the pollen grains. When you see the pollen billowing off a tree that has just ‘popped,’ or opened its cones, it looks very similar to smoke coming from a wildfire.”
