Birch Tree Allergy: Pollen is in the Air!
Do you see them? The catkins on the birch trees are a sure sign of spring and a warning to all those birch-allergic patients. The catkins are those long pendulous structures drooping from the small branches. Each male catkin can release 6 million pollen grains in a season! (it only takes a few hundred to trigger an allergic reaction)
Belong to the Betula species. There are 50 species worldwide and 15 species are native to North America. River Birch has the most southerly range. The yellow birch tree is the largest Eastern birch found commonly in Canada and the Northeastern U.S. In fact, birch trees are plentiful from Alaska and Canada southward. These trees prefer to grow in direct sunshine and not shade. Birches are rapidly growing but their lifespan is relatively short at about 50 years. The bark is characteristically thin with lenticels (dark horizontal lines). The leaves are alternate, ovate (wider at one end) or triangular and doubly serrate (notched or tooth like).
Birches are used for wood pulp and lumber. Native Americans used birch bark to make canoes and wigwams. Sap from the birch tree can be boiled to make syrup or fermented to make an adult beverage (Birch beer).
Birch trees are wind-pollinated. Pollen and seed catkins are on the same tree. The male catkins are formed in late fall and appear as stiff fingers on long shoots that elongate and become pendulous in the spring. Birch trees release enormous amounts of pollen in the early spring. This occurs just before the leaves unfold. Anthesis (time when the flower is fully functional) occurs from February into May. Birch pollen under the microscope is usually triporate (3 pores or holes). Each grain is between 20 and 27 micrometers in size (1/1000 inch). (This is about the size of a wool fiber or 3 times wider than a human red blood cell)
The pollen can trigger spring time allergic rhinitis (hay fever) and even asthma.
Pollen-Food Allergy Syndrome:
Many individuals with birch pollen allergy will also experience mouth or throat itching and mild swelling when eating fresh apples. This is due to the cross-reactive heat sensitive protein. When the apple is cooked (apple pie or apple sauce), the protein is denatured (broken down) and symptoms do not occur.
At Family Allergy Asthma & Sinus Care, we enjoy teaching our patients the finer points of the triggers of their allergies. You may even find yourself becoming interested in botany (plant science). If you are suffering from spring allergies, call us at 704-817-2022 and make an appointment.