Regional Issues  
Prevalence of allergy and asthma in the Southwest

Moving to the Southwest for Health Reasons?  
Asthma / Respiratory allergy / Climate, mold and mites / Pollen /Air pollution 
 

Asthma 

• Asthma may improve after moving to smaller cities in the arid Southwest 
• Improvement may be from escaping high mold spore counts or high dust mite counts 
• Improvement may follow move from heavy polluted environment 
• Very severe asthma does not usually improve: don’t move for this reason alone 
• Some asthmatics may do better in Tucson than in Phoenix and Yuma, where mold counts  are higher. 
• Consider a trial period of several weeks in the area. 

Respiratory Allergy 

• Includes allergic rhinitis and asthma 
• Some very allergenic plants such as short ragweed and giant ragweed don’t grow in the Southwest 
• Many of the pollen-producing plants that grow in the Sonoran Desert are different from those in other regions
• Allergy can develop for the first time because of contact with pollen unique to the area, often after a "honeymoon" period of 12-18 months 
• Allergy testing to southwest allergens: delay for at least 12 months after moving 
• Allergy injection treatment for cold climate pollen: stop unless the move to the desert is temporary 

Climate, Mold and Mites 

• The Southwest is dry: only 10 inches of rain per year, most in the summer “monsoon” (June 15 - September 30)
• Less cultivation and irrigation in rural areas keeps mold spore counts down 
• Humidity and airborne mold spores increase after summer rain 
• In homes with refrigerated air conditioning: house dust mites are a relatively minor problem 
• House dust mites and other indoor allergens are more prevalent in evaporatively cooled homes due to higher indoor humidity 

Pollen 

• Maximum pollen counts are lower than in most other regions in the USA 
• Flowering periods are longer: pollen in the air almost year-round 
• Pollen counts are lowest in December, January and July (see Tucson Pollen Calendar) 
• Bermuda grass produces the most important allergenic pollen 
• Allergy to pollen from cool climate grasses does not cause allergy to Bermuda grass.  Many other grasses in the Southwest do crossreact with cool season grasses
• Allergy to unique pollen types in the Southwest takes time to develop (see Allergenic Pollen in  the Southwest).                 

Air Pollution 

• Little heavy industry in Tucson: most pollution from dust and motor vehicles 
• Phoenix has heavy pollution and Las Vegas expected to have similar problems soon 
• Tucson and Albuquerque are less polluted than larger cities (see  Air Pollution, Asthma and Allergy) 

Travel - see AAAAI site Traveling with Allergies and Asthma
 

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

Updated 9/ 2008