Cedar: The Allergy Plague of Trees

Why call Cedar a Plague?

Junipers (aka Cedars), are causing enormous problems for central Texas.  For example, the area of infestation in Texas already has a terrific problem with water shortages throughout the year. During years when rainfall is less than normal (approximately 30 inches), the juniper is absorbing ground water at an alarming rate.  For the outdoors people, the juniper overtakes areas that would normally be in native hardwoods and grasses and ruins the area for outdoor enjoyment.  However, another serious area of concern for people is the pollen production that occurs each winter.  This pollen production is the major culprit for allergy sufferers to seek refuge indoors and with heavy medication.  The juniper really has no redeeming value: it is poor firewood, it is poor landscape plant, it is a poor source of food for native animals and it is poor wood for construction.

In the following paragraphs, the negative aspects of juniper are covered more completely.

The Cedar Allergy Problem

The Allergy, Asthma and Immunology Clinic of Georgetown, Texas has a web site describing the awful effects of cedar allergies http://hovanky.com/allergy/mountain.htm .  From December through February, many people experience an itchy, runny nose, sneezing, nasal blockage, excess tearing and itchy eyes. Others complain of itching of the palate, throat, or ears, and postnasal drainage. Some have fatigue, mild headache, facial discomfort, sore throat, partial loss of sense of smell, and sensation of ear plugging. If you experience the above symptoms every year during these months, the chance is great that you have Mountain Cedar allergy. Allergy sufferers often describe an obvious seasonal pattern of the onset of symptoms over the years. This condition is mostly caused by pollens. Throughout the northern hemisphere, tree pollens appear from March through May; in central Texas, these are mostly pollens of: Ash, Oak, Box elder, Hackberry, Sycamore, Walnut, Elm, Hickory, Pecan, Mesquite, and Mulberry. The exception is with the Fall Elm (or Cedar Elm) tree which pollinates in August, September, and October. The grass pollen season extends from May through August. Weed pollens are observed from July through October. Therefore, for most parts of this country, the atmosphere in the winter months is usually free of pollens. However, central Texas has pollens of Mountain Cedar in the winter months. For example, in Georgetown, the Mountain Cedar pollen count rose from zero on November 3, 1998 to 300 pollens per cubic meter on December 8, and to 4,890 pollens per cubic meter on January 2, 1999.

The culprit is the member of the cypress-juniper (Cupressaceae) family, the Mountain Cedar, Juniperus ashei (also called Juniperus sabinoides or Juniperus mexicana). It grows naturally and is the most allergenic tree in Central Texas. The Mountain Cedar (MC) is an evergreen tree with grey-brown shredding bark, it grows to a maximum height of approximately 30 feet on the limestone plateaus of central Texas, and in smaller favorable areas of Texas, New Mexico, northern Mexico, Arkansas, and Oklahoma. The Junipers have male and female plants, At the ends of its scalelike leaves, the male tree proliferates numerous reddish-brown cones 3 to 4 mm in diameter tipped with pollen, while female trees bear fewer 6 to 8 mm diameter dark blue-green berries (cones). The pollens from the male tree appear as smoke in the air if the branch is physically disturbed. Juniperus ashei (Mountain Cedar) dominates most of the Edward’s plateau hill country of central Texas; the trees have become overgrown and a pest for farmers and ranchers.

The Mountain Cedar generally pollinates from November through March with the heaviest pollination during December, January, and February. During this period of heaviest pollination, Mountain Cedar is the only pollen present in significant amounts in the atmosphere of central Texas. This toxic pollen is important particularly to those migrants who have never been exposed to it. Many patients correlate their symptoms with Christmas Day. National Allergy Bureau (NAB) data shows that in central Texas, mountain cedar pollens appear as early as October, peak in January, remain elevated until April, and are occasionally seen as late as May.

Mountain Cedar Pollen


The pollen is very buoyant and may be carried by the air for miles. Among all the junipers, the mountain cedar has received the greatest attention as an allergen source. The toxic nature of the mountain cedar pollen may lie in its chemical nature. The allergic reactions to mountain cedar pollen appear to be attributable to a single, stable, glycoprotein, with high carbohydrate and low protein content. This contrasts with the majority of known allergens in pollen grains, which tend to be a mix of allergenic glycoproteins having much lower carbohydrate content. The high carbohydrate content in combination with high density make the pollen of Mountain Cedar unique in causing allergic rhinitis.

In addition to making a person feel ill due to allergies, this condition can interfere in a variety of ways with carrying out one's day to day responsibilities. Loss of sleep, limitation of activities, diminished productivity, poor concentration, emotional distress, irritability, fatigue, and practical problems such as repeated nose blowing and nose rubbing, all impact negatively on ability to carry out physical, social and work/school responsibilities effectively. Similar to other pollen allergens, mountain cedar pollens contact the lining tissue of a person's eyes, nose, and lungs. Therefore reducing the duration of exposure to these pollens is important.

Also, from the Intellicast web site, there is even more to say about cedar and its affect on humans in their segment on Cedar: Midwinter Allergies If you live in Texas, and you have allergies, you probably suffer from cedar fever - the dreaded allergy symptoms brought on by the pollinating cedar tree each winter. Despite the name, you don't actually get a fever. Instead you get itchy, watery eyes; runny nose; and sneezing.

Cedar trees, also known as juniper trees (officially called Juniperus ashei), are evergreens that are predominant in Texas, especially the cities of Austin and San Antonio. The mountain cedar tree is the main culprit of allergies in Cedar Valley (named for its abundance of cedar) and the Texas Hill Country. But Texans are not the only sufferers. Many Western states have areas rich in cedar, including Colorado and New Mexico. In fact, because of the large allergy problem in Albuquerque, the city banned the growing, selling, importing, or planting of cedar trees. (Violators are fined up to $500.)

Though most trees pollinate in the spring, cedar trees pollinate in December, January, and February. If you live in cedar country, your best defense against pollen is to stay indoors as much as possible.

You can't hide from the pollen completely, but there are steps you can take, even when indoors:

  1. Keep your doors and windows closed. Run the air conditioner when the pollen is extremely high.
  2. Cover your air conditioning vents with cheesecloth to help filtrate the pollen, and change the air conditioning filter often. You may want to use a HEPA (high efficiency particulate air) filter to help filtrate the pollen even more.
  3. Dust your home with a damp cloth, and vacuum carpets with a vacuum equipped with a HEPA filter each week.
  4. Take a shower and change your clothes after being outdoors for a long period of time. This will protect you from pollen that lands on your clothes and in your hair.
  5. Bathe pets often, even if they live indoors.
  6. Take allergy medicines exactly as prescribed. If you know cedar will be a problem for you each winter, see your doctor in early fall to update your treatment plan and stock up on prescription allergy medications.
  7. And, eliminate any male cedar trees in your yard by replacing them with good hardwoods like elm, ash, or oak.

If you must go outdoors, pay attention to pollen counts. Peak pollen production is between 5 a.m. and 10 a.m., and pollen counts are highest on warm, sunny days. If you do go outside, wear a painter's mask to cover your nose and mouth. When driving, keep your car windows up, and set your air conditioner on recirculate.  The best times to venture out are on cool, cloudy days or during and right after a rainfall. This is when pollen counts are typically lowest.

The cost to our productivity caused by allergic rhinitis from pollens, including cedar, can’t be understated.  On The Allergy Prevention Center web page, http://www.allergypreventioncenter.coml, there is reference to twenty-five cities that have serious allergy problems. The Texas cities referenced list cedar as one of the main allergy culprits.  "Dr. Robert Overholt, an allergist in Knoxville, Tenn., said nasal allergies are responsible for 3.8 million lost school days and workdays every year. Many attacks of nasal rhinitis, also known as hay fever, are often misdiagnosed as a cold, Overholt said. Allergic rhinitis is one of the most common chronic diseases in the United States, affecting 10 percent to 30 percent of adults and up to 40 percent of children -- or somewhere between 20 million and 40 million people."(Source: Dr. Koop Health News)


Dr. Edward G. Brooks, University of Texas Medical Branch, is a Pediatrician with clinical training in allergy and immunology and research training in basic immunology and immunogenetics. Dr. Brooks joined the UTMB faculty in 1993 and became a CHRC young investigator.  One of his areas of research is Characterization of Allergens from Mountain Cedar Pollen.

Mountain cedar pollen is a common cause of allergic pollinosis in central Texas and many other parts of the country and the world. Diseases caused by pollen, including allergic rhinitis and bronchial asthma, are a major health care problem. The cloning of proteins that react with IgE and cells involved in the allergic response is a basis for understanding and treating these diseases.


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