There are a number of problems concerning air-borne allergens peculiar to the Southwest. These are here presented in the form of general observations with the purpose of acquainting allergists of other areas, that they may be better able to advise their patients migrating to or visiting this region.
Geographically, the Southwest is west of a fairly straight line dropped due south from Omaha or Des Moines into the Gulf of Mexico. This line, passing to the east of Tulsa, Okla., and about midway between Dallas and Houston, Texas, is the 30 in. annual rainfall line. The east-west line is a variable curve, varying from year to year, below which there are late freezes and frosts, long hot summers with little rainfall, and short mild winters with temperatures rarely going below 20 F for a day or two at a time. Rainfall is rather concentrated in early spring and fall, with