Airborne grass pollen probably is the most widespread causative agent in allergy, with exposure occurring during much of the year. As is true of most tropical and subtropical areas, few trees shed significant amounts of wind-borne pollen; acacia, eucalyptus, or "Australian pine" (Casuarina) pollen is, however, occasionally suspected of causing an allergy. Fungus exposure is prominent both indoors and out of doors and is responsible for symptoms in many allergic persons, j

When allergic people travel or move to other regions of the country, their symptoms may change, and most often these variations are caused by regional differences in pollen-producing plants. Other factors, however, including airborne fungus spores, algae, and insect fragments, as well as food components, also can vary from place to place and affect a patient’s health accordingly. At times, desired symptom improvements do not occur despite carefully planned major geographic moves. In effect, allergens from domestic dust, bedding, upholstery, and house pets accompany the patient and continue to provoke illness in the new surroundings. These factors, reflecting household practices and life style, have indoor or job-related sources and can be effectively eliminated by applying practical environmental measures. Allergic symptoms also may recur in distant places because of acquired sensitivity to allergens (for example, pollens) unique to the new area. More often, the disappointed patient has simply not yet left the range of an offender allergen despite a journey of hun­dreds or even sometimes thousands of miles. As many grasses and tree species, for example, grow throughout the continent, avoidance of their pollens is difficult and requires careful selection of refuge areas. Thus, permanent geographic moves to change allergen ex­posure should not be undertaken impulsively. They might be con­sidered after successful trial periods in the area under consideration. While allergic problems may be difficult to predict in a new area, some estimate of expected allergen exposure is possible. The follow­ing charts should assist such speculation as well as indicate the al­lergens that may produce recurrent symptoms in established regional populations. To simplify reference, groups of states and bordering Canadian provinces with similar climate and pollen allergens are considered together. As the resulting groupings are large and not strictly uniform,
these charts only describe average conditions. Points close to a boundary between two areas will, of course, have allergens typical of both. For each region, important hay fever plants are listed with the time of pollen shedding for each indicated with respect to the calendar year, with the horizontal bars across the columns indicating the time of the allergen occurrence. Plants that are mostly cultivated are marked (C), and sources restricted to part of a region are de­noted by (N) North, (S) South, (E) East, (W) West, (L) Local, and (NW) Northwest. In each table, noteworthy pollen-producing trees are noted first, followed by grasses, and broad-leafed plants without woody stems (or weeds). For each type, an approximate indication of the im­portance of an allergy offender in the overall region is given on a scale ranging from ± (minor) to -| —1—|- (very major). The reader should understand that these appraisals are overall averages for entire regions and their allergic populations. Differ­ences in individual sensitivities and the local distribution of sources (such as pollen-producing plants) may convert a generally unim­portant pollen type into a major cause of symptoms. Other factors —Pine, spruce, fir, and hemlock pollens are released in large amounts but are not proven factors in hay fever and asthma. Some ragweed occurs where the forest has been disturbed. Fungi— especially mushrooms and puffballs—are abundant (June-October) but seem to cause only limited symptoms. Cabins and cottages that have been left closed for many months and that are often not fully watertight tend to be moldy. Tables on pages 140-153 adapted from material originally appearing in A Manual of Clinical Allergy, J. M. Sheldon, R. G. Lovell, and K. P. Mathews, editors and reprinted by permission of W. B. Saunders, Philadelphia, PA. Copyright © 1953. Other factors —Insect scales and hairs may provoke symptoms in such localities as inland lakes where certain types swarm seasonally. Fungi are important factors from May to November, especially in grain-growing areas; exposure increases whenever vegetation or soil is disturbed. Plants that process seed materials—such as castor bean, cottonseed, and soybean—may release dusts that cause allergic reactions. Other factors —Fungus exposures can produce symptoms during much of the year. High humidity encourages fungus growth and may directly affect respiratory symptoms.







Other factors —Pollens from eucalyptus, Brazilian pepper tree, palms, and other cultivated trees occur but are probably minor factors at most. Fungus spores in moderate numbers are airborne throughout the year, and indoor fungus growth is fostered by the continuously high relative humidity.

Other factors —Extensive livestock operations provide local sources of animal dander exposure. In addition, dusts from fertilizers and animal feeds, as well as from grain-storage facilities, can create serious allergic problems. Cultivated areas are especially important sources of fungus spores from early summer to the first snowfall. Other factors —In this region, huge amounts of pollen are released by conifers—including pines, spruce, fir, and hemlocks—but their effect on allergic people remains in dispute. Fungus spores derived from field crops are less abundant than in areas located farther east. Other factors —In hilly areas, birch, aspen, and oak pollens may cause seasonal allergy. Fungus exposures are only rarely a source of major symptoms.






Other factors— Pollen produced by tamarisks and mesquite or by plantings of castor bean, pecan, or eucalyptus may, in rare instances, produce respiratory allergy. Fungus exposures are relatively low, although extensive irrigation promotes fungus growth. The use of evaporative ("swamp") cooling units in buildings increases indoor fungus exposure, although the risks involved are not precisely known. Other factors —The effects produced by eucalyptus, coast maple, 1 and acacia pollens are unknown. Fungus exposures vary from mild to moderate according to the density of local plant cover. Other fa
ctors —Areas devoted to grass-seed production may ex­perience high grass-pollen levels as a result. Large amounts of conifer pollen are shed, especially at higher elevations, but they are generally of uncertain importance in allergy. Respiratory illnesses, including asthma, are associated with wood industries, most notably where western red cedar is processed. Fungi flourish in humid coastal areas; the types present, however, seem to cause milder symptoms than does exposure in grain-growing areas of eastern regions.

Respiratory allergy is, at most, a minor problem for persons living in arctic and subarctic areas. In most areas, brief periods of pollen-shedding by birches, alders, and willows precede a short grass-pollen "season." Although the levels of fungus spores seem to be compara­tively low, animal dander, especially dog dander, often is a prominent exposure factor throughout the year.

Clearly, grasses are the major source of pollen allergy, regardless of the time of year. Also, significant levels of fungus spores, accom­panied by allergic symptoms, occur in all the seasons. It is suspected, too, that insect-derived material plays a role in allergies. One source ; of insect debris is the droppings of bats, which often live in the roofs of private homes. It is not clear, though, whether the droppings con­tain bat dander. Respiratory irritation from the smoke of burning sugar cane is widely recognized, but a true allergy to the smoke has not been proved.