MNN Galleries

11 allergy-inducing pollen producers

April 21, 2011, 7:30 a.m.
Pecan pollen

Photo: Clearly Ambiguous/Flickr

5 of 13

Hickory (pecan)

Pecan trees like this one make more than just sturdy timber and nutritious nuts. They're also major sources of allergenic pollen, and they aren't alone: At least 11 other hickory trees also cause severe pollinosis, including the bitter-nut, mockernut and shellbark hickories.

Habitat: Eastern and central U.S., Mexico, Canada, China, India and Indochina

Description: Tall trees with wide, straight trunks that can reach 100 feet high

Allergenicity: Severe

Allergy season: Late spring (April to June)

Tips: Hickory trees are monoecious, which can make their pollen hard to escape. Fortunately, the large particles don't travel very far and are less prevalent in the afternoon.