UA logo Allergy and Asthma in the
Southwestern United States
Information for patients with allergy and related problems
in the Southwest

Environment and allergic disease                     Return to menu

Southwestern Deserts 

  • The Sonoran Desert extends from Sonora, Mexico into Southern California and southwestern Arizona.  Population centers include Phoenix, Tucson and Yuma, Arizona, and Hermosillo, Sonora. 
  • The Mojavean Desert lies in Southern California and southern Nevada.   Las Vegas is in this area.
  • The Great Basin or Sagebrush Desert extends from Nevada into western Utah.  Salt Lake City, Utah lies on the eastern edge of this desert, Boise, Idaho in the north and Reno, Nevada on the western edge.
  • The Chihuahuan Desert extends from southern New Mexico and West Texas into the east of Northern Mexico.   Las Cruces, New Mexico,  El Paso, Texas and Juarez, Chihuahua are in this desert.

These deserts are arid or semi-arid and have an annual rainfall between 3 and 15 inches.  Atmospheric mold counts are usually very low, except in intensively irrigated areas.

The flora of these deserts are very diverse, including a large number of wind-pollinated species such as several species of Ambrosia (bursage, ragweed), several species of Atriplex (saltbush, scale), several Amaranths (pigweeds), mesquite and creosote bush.  Sagebrush is widely distributed and most prevalent in the Great basin.   Mesquite and Cottonwood are prevalent in drainage areas.  At higher elevations that border the limits of these deserts in Arizona, Southern California, Utah and New Mexico, wind-pollinated plants include sagebrush, juniper and oak, and at the highest elevations, spruce, fir, cedar and pine.    Allergenic trees in riparian areas include cottonwood, alder (in mountains), Arizona ash, and sycamore. 

The Urban Environment

Cities and their freeways in the southwestern desert have been growing fast in recent decades and have contributed to the increasing urbanization of our population.  This has resulted in increased exposure to pollution including ozone, NO, and fine particulates which have correlated with increasing prevalence rates of asthma. 

As in most cities pollen types in urban areas of Phoenix and Tucson hae been affected by introduction of non-native plants and trees, some of which are allergenic.

Although Southern Arizona has a dry climate and consequently low airborne mold levels as compared with other parts of the US, the effects of climate change on mold and pollen levels should become an important field of study in the near future.

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Disclaimer:   This site is for educational purposes only.  Any information that you have found in this web site is not intended to replace medical care or advice given to you by your own physicians. You should consider consulting your local medical library and other web sites for additional information. 

Comments and suggestions welcome!   Email: schumach@u.arizona.edu
Content Owner:  Michael J. Schumacher, MB, FRACP, The University of Arizona