FROM 1873 to 1916 both the medical profession and the population of hay fever sufferers were content to rely on hearsay concerning hay fever conditions through-out the United States. Interest in the subject of geographical distribution of hay fever centered about locating hay fever resorts. From the time of its origin in 1873, until its dissolution, the members of the United States Hay Fever Association dedicated themselves to this task. Their efforts toward discovering hay fever-free areas consisted of trying different vacation grounds from year to year. Whenever a member of the Association obtained relief from his symptoms in a new locality, it was his bounden duty to report it to the organization.
The activities of these members. comprised the sum and substance of organized endeavor for half a century, in exploring the presence or absence of hay fever weeds in the United States. Such indolence is not readily comprehensible, especially when we consider that Charles Black-ley described in 1873 the present day method employed in studying atmospheric pollen concentrations.
About fifty years later Blackley’s suggested method was applied by Dr. William Scheppegrell in pollen studies in the State of Louisiana. Following this, examinations of pollen conditions were made in several cities. However, the first extensive scientific survey of hay fever conditions was not undertaken until 1928. This investigation was instituted by Oren C. Durham, the foremost present day botanist in the field of hay fever. His method of study which has continued until the present was well planned and scientific. It consisted of atmospheric examinations supplemented by field studies. To accomplish the atmospheric investigations, vaseline coated slides were placed at various Weather Bureau Stations in the United States. They were exposed daily, throughout the year or during selected seasons covering the most important hay fever periods. Samples of the pollens in the air in each locality were thus obtained.
Each slide was sent to Mr. Durham who identified and counted the pollens. In this manner information was gathered showing the onset, apex and close of the hay fever season of each kind of active hay fever pollen in the various localities. By arithmetic computations and comparisons, standards were set up to determine the extent or degree of pollen concentrations in any locality. Graphs such as appear in Fig. 13 were prepared for each area tested. A glance at the graphs shows, for instance, that Indianapolis experiences atmospheric concentrations of ragweed pollens that are ten times as great as that of New York. Nevertheless, the standards worked out by Durham indicate that even the low ragweed pollen concentrations of New York are high enough to cause symptoms in the average hay fever sufferer. At the same time the graphs indicate to the doctor that a ragweed hay fever sufferer in Indianapolis needs ten times as much protection against pollen concentrations as a sufferer who is going to live in New York during the ragweed hay fever season.
The graphs and pollen counting studies deal largely with ragweed because it is by far the most important hay fever factor in America. Computations based on these studies are valuable because they supply us with reliable information as to the nature of ragweed hay fever conditions in various areas. For instance, on the basis of his experience with pollen counts and field observations Durham estimated that a concentration of 25 or more pollen grains of ragweed on a unit area of the slide is considered high enough to cause symptoms in the average ragweed sufferer. This figure is then used to determine the number of hay fever days in any locality. In this way we have an accurate method of verifying the verbal reports of individuals whose opinions are based merely on their own subjective judgment.
Pollen counting studies have been conducted in hundreds of localities since this first survey. By 1935 extensive data on Canada and parts of Mexico were obtained. More recently, reports have been received from workers in Argentina, Brazil, Hawaii, Honolulu, and Palestine.
From this apparent expansion of interest, it would seem that accurate knowledge of hay fever conditions through-out the world is readily available. This is not the case. Actually, there is a paucity of such information. Even here in the United States there are literally hundreds of localities that are yet to be investigated.
In the interest of the millions of hay fever victims, the departments of Health or Agriculture in every State and City of the United States should survey its environs with reference to hay fever pollens. With but few exceptions, city and state officials have given little thought to the hay fever problem. Letters sent by the author to the Departments of Health of the forty-eight States brought replies from all of them. In their replies more than half of the officials indicated that no survey of hay fever conditions had been made in their state. Two of the States, namely New York and Michigan, sent results of ragweed pollen counting experiments in selected portions of their State.
Despite the absence of State sponsored surveys, the unheralded efforts of Oren C. Durham and others has changed our knowledge on hay fever conditions in North America from guesswork to scientific accuracy. By gathering the results of their labors we are able to present a partial picture of hay fever and its many geographical relations. We shall review the status of hay fever conditions in cities, at the seaside, on islands and in the mountains. To this will be added a variegated representation of the hay fever situation in more remote areas as Mexico, Alaska, Canada, Central America, South America, and Europe.
HAY FEVER IN NEW YORK AND OTHER CITIES
Hay fever has been termed a disease of civilization. This observation is reflected in the great prevalence of hay fever pollens in and about most of the well populated cities of the United States. In contrast to this, extensive forests and uninhabited virgin territories are usually found to be free of hay fever weeds.
It is a strange paradox that city people go to the country while country people often journey to the cities in an attempt to find relief from hay fever. One of them must be wrong. The country dwelling hay feverites who travel to the city for relief quickly learn the error of their judgment through sad experience.
Thickly housed centers like New York, Boston, Philadelphia, and Chicago receive more than their share of ragweed pollen. In the residential and business districts of New York City, the tall buildings and absence of vegetation are slight protection against hay fever effects. The aeronautical characteristics of buoyant pollens bring a full quota of hay fever to Times Square, the heart of the non-vegetative section of New York. It is a simple matter for the offending pollens to travel a distance of five to ten miles from Brooklyn, New Jersey, the Bronx and Long Island in which localities the responsible weeds grow abundantly. And the tall buildings can’t stop these pollens that scale 2000-foot mountains with ease.
Pollen counting studies in the business sections of New York, Chicago, Detroit, Cleveland, Buffalo, New Orleans, Houston, Milwaukee, Indianapolis, and Pittsburgh, has disclosed large concentrations of pollens in these areas. The pollen effects are severe enough to cause suffering among these city residents for periods varying from two weeks to six weeks.
A recent investigation of ragweed conditions in Maine gave interesting results. Greater pollen concentrations were found to exist in the vicinity of the cities in the agricultural areas. The explanation is found in the fact that plots and fields near the cities often remain uncultivated thus inviting the growth of weeds. An additional factor is the usual growth of ragweed in the ditches and road-sides along automobile routes of travel leading into the cities.
From what has been said, it is quite clear that you can not expect to find relief from hay fever symptoms in the confines of city limits which are located within a radius of twenty to thirty miles of abundant ragweed growth.
HAY FEVER AT THE SEASHORE
A summer vacation -at the seashore is not insurance against the ravages of hay fever pollens. You will often be advised to go to. the seashore for your hay fever. Such action is inadvisable unless you first investigate the offending plant conditions in the particular locality.
To the uninformed it may appear that seaside resorts would be natural hay fever resorts as well. However, experience has indicated that such a generalization is for the most part erroneous. A moments reflection on what has been said about winds and pollen buoyancy should be evidence enough. Aside from the influence of prevailing winds, we have often found an abundance of ragweed plants in the empty lots and neglected plots of popular beach resorts.
Pollen surveys have been conducted in several seaside areas. For example, on the east coast, Atlantic City has been indicated to have a high enough pollen concentration during August and September to yield what is termed eighteen days of hay fever.
One of the most complete pollen surveys ever conducted under the auspices of a State Department of Health was carried out in Michigan. During the summers of 1940, 1941, and 1942, pollen slides were exposed at 50 stations in the State of Michigan. Of the seaside localities, Grand Haven, Ludington, Manistee and Benton Harbor, all contained definite pollen concentrations high enough to yield fifteen or more hay fever days. Every one of these cities is located directly on the water front of Lake Michigan.
Durham and Sylvester found the seacoast town of Port-land, Maine, to have eighteen days of hay fever in 1937.
Boston, another Atlantic Coast city has two to three weeks of severe hay fever conditions every year.
A SUBJECTIVE SURVEY
The writer conducted what may be considered a subjective or field examination of ocean front or seashore re-sorts along the Atlantic Coast from Maine to Virginia. The method was threefold. At least one doctor was interviewed in each area concerning the prevalence of hay fever; a search for the ragweed plant was made in every locality; and persons known to suffer from hay fever were questioned whenever found.
Our report on east coast seashore resorts is most discouraging. At every one of the resort towns visited we found definite evidence of fall hay fever lasting for at least one week and generally longer. Rockaway Beach, Long Beach, Coney Island, and Brighton Beach, in New York, were indicated to have about as much hay fever as exists in the City. Asbury Park, Point Pleasant, Seaside Park, and Beach Haven, in New Jersey, showed the presence of ragweed pollens lasting into September. Other localities which gave varying evidences of hay fever included New London, Mystic, and Port Chester, in Connecticut; Westerly, in Rhode Island; Virginia Beach and Norfolk, in Virginia; Portsmouth, in New Hampshire; and Old Orchard Beach and York Village, in Maine. For this type of investigation we have little respect and heartily recommend that our casual technique be checked by a more efficient and thorough pollen counting study.
It should not be concluded from the above that seashore resorts or seaside towns per se, are unfavorable as hay fever resorts. Our purpose is to foster the growth of more exact knowledge about these and other localities to which hay fever sufferers are indiscriminately sent for relief. Toward the realization of this goal we can only repeat that additional scientific pollen surveys need to be conducted.
THE ISLAND REFUGE
The status of hay fever conditions on coastal islands in the United States is very much akin to that of seaside towns. Hay fever sufferers have long imagined that any island would represent a haven of refuge against their suffering. This has not been the case. It is unfortunate that most of the habitable islands in the favorable climates of the United States are near ragweed-laden mainlands. Studies have indicated quantities of ragweed pollen in the air at Plum Island, Wisconsin; Fire Island, New York; Block Island in Rhode Island; and Nantucket Island, off the Atlantic Coast of Massachusetts. Pollen concentrations on these island Iocations were bad enough to cause hay fever symptoms for periods of ten to twenty days.
In general, you can expect to find the same type of grass vegetation on the islands as occurs on the mainland nearby. With winds blowing from the direction of the mainland the pollen concentrations on coastal islands will be high and will cause hay fever among sensitive victims living on the islands.
Escape from grass pollens is not easily accomplished. However, it is reported that the islands of Bermuda offer a safe refuge to grass and ragweed hay fever patients. A pollen survey of Bermuda has indicated exceptionally low grass pollen counts and no ragweed pollens at any time. But if you are sensitive to the pollens of the cedar tree stay away from Bermuda between March and April. The authors of the reported survey recommend Bermuda as a hay fever resort for persons sensitive to ragweed, grass, and plantain pollens. They point out that the islands of Bermuda are only forty-two hours by boat and four hours by plane from ,New York.
If you care to go further toward tropical climates you can obtain relief from hay fever in the Islands of Hawaii and Honolulu. Although pollens of redtop, sugar cane, and Bermuda grass are found on these islands they are never seen in large amounts.
HAY FEVER IN THE MOUNTAINS
Misinformation concerning hay fever conditions in mountain areas is more prevalent than accurate knowledge on the subject. It is not difficult to realize from whence our false ideas have stemmed. Behold the United States Hay Fever Association and its meeting grounds, namely, the White Mountains.
Ask any well meaning friend or doctor in the East and they will tell you that the White Mountains are hay fever-free.
You might forgive being misled by your friend but not by your doctor. But then we can’t blame him too much, for most books on hay fever that the doctor has read, mentions the White Mountains as the hay fever resort area of the United States. Not to exonerate the doctor entirely, the truth of the matter is that the medical profession has given little thought to the location of hay fever resorts. A recent medical book on Allergy includes an antedated list of resorts where sufferers reported having found immunity. The list was compiled by William Patterson, the ex-president of the United States Hay Fever Association. We cannot readily understand what purpose is meant to be served by such a list. It includes many places that have since been shown to be loaded with ragweed. It places in a false light some localities that have been indicated by Durham’s more scientific studies to be excellent hay fever resorts. As might be expected, the list includes sixteen localities in the White Mountains, some of which we know to be good and others not so good.
THE WHITE MOUNTAINS
Surprisingly enough, the only town in the White Mountains for which a pollen count has in recent years been reported, is Bethlehem. The slides exposed at the Bethlehem station indicated three days of hay fever in 1935. Mr. Durham admits obtaining second hand information that ragweed was not present within five miles of the town. I should like to offer first hand information, that since 1938 ragweed has been present in the roadside and in the fields within less than a mile of the town. And from my observations it seems to be increasing from year to year. If the ragweed situation is not attended to, the town may lose some of its present value as a hay fever resort.
Conditions in Bethlehem notwithstanding, there are literally dozens of places in the White Mountains where a full dose of hay fever can be had. On the other hand there are a half dozen places which are as good or better than Bethlehem in the amount of relief that one can obtain from the effects of ragweed pollens. On a par with Bethlehem, and located nearby, is Bretton Woods, Twin Mountain and Fabyans. In the same class is Dixville Notch, located about seventy miles further north.
THEORIES ON RESORTS IN THE WHITE MOUNTAINS
The earliest sufferers from ragweed hay fever and pollen asthma obtained truly magical relief at Bethlehem from the effects of their ailment. It was magical in the sense that no other satisfactory means of protection had yet been developed. Sufferers had to rely on drugs and successful escape. The effects were even more remarkable because they were attributed to some unknown powers of the air in that region.
To merely say that no ragweed exists in the locality is inaccurate because ragweed is present in the area.
Many theories have been advanced to explain Bethlehem’s kindness to hay feverites. From our observations we hold the following theory. Due to the low mean temperature, late spring thaw, frequent late summer frosts, followed by an early fall frost, the ragweed does not have an opportunity to pollinate for any effective length of time. In addition, the central location of Bethlehem in the heart of the White Mountains, surrounded by four groups of mountain ranges, makes it difficult for the pollens to be carried into Bethlehem, which is itself a shelf on Mount Agassiz.
HOW TO FIND A WHITE MOUNTAIN RESORT
In the absence of pollen counting studies we will have to generalize about the White Mountains on the basis of our own subjective observations.
In a search for localities in the White Mountains that might be free of ragweed pollen contamination we were guided by the following hypothesis. The area should have an altitude of about 1400 feet; be next to a lake; and be located at least as far north as Portland, Maine, or Lake George, New York. By stipulating that the place is on a lake we have reasonable certainty that it will be surrounded by mountains; and the more mountains around it, the better. An altitude of 1400 feet plus northerly location in this region, yields a low-average temperature which acts to impede profuse ragweed maturation. With reference to this point, we have frequently seen unmatured ragweed in the White Mountains as late as September.
The conditions we outlined are, of course, not absolute. Large unbroken forest areas offer as good protection as surrounding mountains and reduce the necessity for high altitudes. Higher altitudes will make up for less northerly locations. And locations in the extreme north will tend to reduce the necessary altitudes.
Thus, we are aware that you and others may know of places in the mountains of our eastern states that do not meet our stipulations but which are nevertheless, free of ragweed. However, our purpose was to set up basic conditions that would tend to insure the success of our finding ragweed-free localities in New Hampshire. We think that our results justified the theory.
Employing our hopothesis we located several regions in New Hampshire that we believe to be free of ragweed hay fever. Our findings are again based on interview, a search for ragweed and subjective judgment.
The hay fever-free areas in New Hampshire that we list for your approval and recommend for check by pollen study include:
The Village of Pittsburgh Lake Francis Back Lake First Connecticut Lake Second, Connecticut Lake Third Connecticut Lake Diamond Pond, Stewartstown Hollow North Dorchester
These localities are not resorts as yet. However, they are habitable and accessible by train and automobile. It has been said that as soon as they become resorts they will become infested with ragweed. We disagree on the basis of the following reasoning. If Bethlehem which has been frequented since 1875 showed only three days of hay fever in 1935, then comparable areas located further north should be free of hay fever for at least fifty years and that’s long enough for us.
THE MOUNTAINS OF MAINE
Maine has long been famous as an eastern vacation land but not as a hay fever refuge. Nevertheless it has characteristics which should recommend it highly as being free of hay fever. It is the extreme northeastern state of the United States. It includes the Blue Mountains and receives the protection of the White Mountains in the west. In its northern part, Maine is studded with lakes and uncultivated virgin forests. Here again if you apply the principles of high altitude, northerly location and presence of a lake you can seek out from the map many areas free of ragweed pollens.
With regard to Maine we need not be guided by hypothesis. Reports have been received on the results of pollen studies accomplished by the efforts of Dr. Sylvester and Mr. Durham. They indicate that the most favorable places are Presque Isle, Rangeley, Greenville and Machias. Four to five days of hay fever are reported for York, Southport, Bar Harbor and Eastport. Our own observations lead us to agree with these findings. However, during a windy summer, the average ragweed sensitive individual will experience more than five days of hay fever in York, Bar Harbor and Southport. We might add that we found Houlton, Caribou, Madawaska, Ashland, and Van Buren, to offer the same hay fever-free benefits as Presque Isle. We would further say that after September 5th almost any place in Maine north of Calais is free of hay fever.
THE GREEN MOUNTAINs
In general, the Green Mountain region of Vermont offers little protection for hay fever sufferers. Applying our formula to Vermont we found a place called West Danville near Joe’s Pond, which seemed to have some merit. However, we located ragweed growing in the region; some of which had begun shedding pollen by August 20th. Strong winds blew pollens into the locality from north and south. Similar places in Vermont about which the same could be said is Averill Lake, and Lake Wallace, on the Canadian Border.
The Mount Mansfield area of the Green Mountains has been indicated by hearsay to be free of ragweed. We would judge Lake Mansfield near Stowe, Vermont, to be the best place in this region.
THE BERKSHIRE MOUNTAINS
The ragweed hay fever situation in the Berkshire Mountains of Massachusetts is about the same as in the Green Mountains of Vermont. Due to its proximity to the lower areas of New York and Connecticut, the Berkshire Mountains are vulnerable to wind borne pollens from these and other nearby areas. The best localities that we were able to find were near Hoosac Lake and Ashley Lake. Adams, near Mt. Greylock also proved to be fairly favorable. However, these conclusions are based solely on our subjective findings. Until checked by pollen counts we cannot speak authoritatively about this region. We are further led to believe that a thorough investigation will reveal several other regions in and near the Berkshires that are located in wooded areas. We might recommend that such a survey be sponsored by the interested summer camp owners in the locality.
THE ADIRONDACK} MOUNTAINS
Concerning hay fever relief that may be obtained in the Adirondack Mountains of New York, we have the reports of some pollen counting observations by the New York State Department of Health. A map issued by the Department indicated favorable conditions in the locality of Blue Mountain Lake, Raquette Lake, McKeever, and Big Moose. The Tupper Lake area seems to have had a variable career similar to that which was previously indicated for Lake Placid. In 1939 there were 6 days of hay fever at Tupper Lake; in 1940, 1 day; and in 1941, 13 days.
The eastern portion of the Adirondack region is considered unfavorable as regards hay fever. Until further investigation is completed, the Blue Mountain Lake region must be thought of as the best area in the Adirondacks for escape from hay fever pollens.
THE CATSKILL MOUNTAINS
Little can be said for, or about, the Catskill Mountains of New York concerning the presence of hay fever. The location of the resort towns in this region are not far north enough to impede ragweed growth. Camps in isolated localities of high altitude and wooded country, may be located in areas of low pollen concentrations.
A map issued by the New York State Department of Health indicates an area of moderate ragweed prevalence. This area is in the mountainous region north of Liberty and south of Fleischmans. If we may venture a guess it is our opinion that without the added protection of ragweed inoculations, few areas in the Catskill Mountains will yield major relief from ragweed hay fever.
THE ROCKY MOUNTAINS
As noted in the section on plants, the hay fever weeds of the Rocky Mountain region include more than just ragweed. Because of the warmer climates in Montana, Wyoming, Colorado and New Mexico, through which the Rocky Mountain range extends, one has to reach exceptionally high altitudes to get above the level of weed growth. As reported in the letter from the Utah State Department Of Health the canyons in these regions seem to be equally free from offending weeds.
In the southern area of the Rocky Mountain region, ragweed pollens are in the air in Phoenix, Arizona, during the spring when the false ragweeds shed pollen. However, the mountainous part of northern Arizona is considered to be relatively free of ragweed pollens.
In the extreme western region, conditions are entirely different. Just beyond the Cascade range of mountains we have Portland, Oregon, and Seattle, Washington. Here a phenomenal situation prevails. In this area, there just aren’t any ragweed pollens. The most sensitive ragweed sufferer can find one hundred percent relief in this area. The prevailing winds are from the Pacific Ocean, and the Cascade Range offers complete protection from desert pollens. Added to this is the fact that the climate is entirely unsuited for ragweeds. This condition prevails on up into British Columbia in Canada.
Allergists state that the best means of protecting one’s self against a particular allergen, consists of complete avoidance. Were hay fever sufferers able to take this advice literally the doctors specializing in hay fever treatment would have to change their specialty. The best means for complete avoidance of pollens is obvious; rent a house boat and live in the middle of the ocean for the duration of your hay fever season. More seriously, however, many persons do take ocean voyages as a means of avoiding the effects of offending pollens.
For tree and grass pollen sensitive persons the ocean voyage is a more difficult escape method. You cannot merely sail to Europe, Australia, or New Zealand, for the offending plants do exist in these places as well as in the United States. Bermuda and the tropical islands may be a happy destiny for grass pollen victims. The last alternative is to take an extended cruise and remain many miles off shore throughout the period of the responsible tree or grass pollination.
If you are sensitive to ragweed you are more fortunate in the matter of an ocean voyage. You can start on a cruise about August 10th and sail directly for Europe or the tropical islands. Here you will be free of any fall hay fever pollens throughout August and September. But before you decide to sail for Europe make sure that you are not sensitive to any of the grasses because there are plenty of them in Europe. Happy sailing if you can afford it.
Cold weather and hay fever are mutually exclusive. Not that the cold destroys the pollens, for it doesn’t. The cold weather does have the effect of killing the weeds and stop-ping their production of pollen.
When we think of cold weather we are apt to think of Canada. Associating cold weather with Canada leads people with hay fever to seek relief there. And those hay feverites who just head for Canada without proper inquiry, or reading this book first, may often be painfully disappointed.
Although politically Canada is a foreign country, geographically it is a northern continuation of the United States. Except in the Great Lakes region Canada is separated from the United States only by an imaginary line seen on maps. Therefore it is not surprising that the southernmost or border parts of Canada are similar to the United States with respect to prevalence of hay fever trees, grasses and weeds.
From Canadian surveys we learn that the northern areas are virtually free of ragweed. If you draw a line across Canada at about the level of Prince Albert or a latitude of 540 you could be fairly certain that all localities north of this line were free of ragweed hay fever. But below this line the story is a very different one; it requires you to look before you leap.
Pollen counting examinations have been made in nine Canadian cities by that tireless investigator Mr. Durham. Of the nine cities Montreal, Toronto, and Ottawa were shown to have from one to two weeks of hay fever during the latter part of August. Port Arthur, Parry Sound and Winnipeg were somewhat better with an average of only five ragweed hay fever days. The best locations were Cochrane, Ontario; Father Point, Quebec; and Prince Albert, Saskatchewan; all three of which were hay fever-free.
In the eastern part of Canada we found by personal examination that the locality from Riviere du Loup to the Gaspe was free of ragweed. Nova Scotia contains some rag-weed, with the greatest concentration occurring in the western part near Annapolis Royal. In general, the hay fever effects in Nova Scotia are light from August 15th to September 1st, after which time they are absent. Yarmouth, on the southern tip of Nova Scotia, has of late become a hay fever resort. We found conditions favorable there, except when occasional strong winds blew from the south-west.
For the far western part of Canada a pollen survey by Dr. Walton gave some rather surprising results in the matter of fall hay fever. Situated near our pollen-free city of Seattle, Washington, one would not expect to find fall hay fever pollens in this locality. Nevertheless, examinations disclosed widespread’ occurrence of Russian thistle and sage in the region of British Columbia and Alberta. Pollen counts of ragweed and sage were rather low but combined with Russian thistle pollens they represented an important cause of fall hay fever.
From April to May there was found the tree pollens of the poplars, hazel, box elder, elm, ash and scrub oak. Grass pollination was observed from early June to the first week in July. Plantain was indicated as an important producer of pollens through most of the summer.
With reference to Canada in general it may be said that the offending trees and grasses are widely and abundantly prevalent. Canada is not a sanctuary against the effects of spring or early summer hay fever. Against fall hay fever many regions of northern and eastern Canada offer excel-lent retreats if selected wisely.
As you might expect from the frigid impression that Alaska creates in your mind, pollen hay fever is as yet non-existent in this region. At least so we can judge from the indications of the meager number of pollens landing on the test slides exposed.
In an effort to complete his pollen panorama of North America the venturesome Mr. Durham explored those distant Alaskan outposts of Nome, Juneau, and Fairbanks. The completion of the Alaska Highway enables one to drive all the way from the United States to these no longer remote regions now protected by American ski troopers. The scientific acumen that led Durham to the Alaskan frontier as early as 1939 must be commended.
MEXICO TO SOUTH AMERICA
Having covered the frigid north let us see what lies in store for the hay feverite in the southern extremes. Entering Mexico at the eastern portion you find giant ragweed and western ragweed in Coahuila and Tamaulipas. Conditions being similar to the southern tip of Texas you can expect two to three weeks of late fall hay fever. At Tampico and Mexico City ragweed hay fever conditions are rather favorable with rare flurries of noxious weed pollens. Tree and grass pollens are more plentiful but seem to be most prevalent in the fall season. It would appear that the further south you go, in Mexico the more improved the hay fever conditions become.
In the parallel latitudes, we have previously indicated that Hawaii and Honolulu are’ entirely free of ragweed pollens. Tree pollens, when produced in great numbers, do cause some hay fever on the islands. Our common grasses are also present but give off very few pollens because of their sparsity.
Proceeding southward through Central America and Panama hay fever is said to be dormant. Entering South America by way of Venezuela, weed pollen conditions continue favorable. In Brazil at Bello Horizonte we learn that there is only one season of pollination. The grasses pollinate here from the middle of May to the middle of June. No ragweed or fall hay fever is reported. Moving into Argentina, hay fever occurring in the late fall is found prevalent in the central parts of the country around Buenos Aires, Santa Fe and Cordoba. The responsible plant is reported to be a shrub-like tree which is related to the hackberries. It sheds profuse amounts of pollen from September to December and accounts for almost half of the huge number of hay fever victims in Argentina.
The other half of the hay fever victims in Argentina correspond to the fall hay fever group in the United States, except that they experience their symptoms from March to April. We say they correspond to the fall hay fever group in the United States because the responsible plant is the well known Russian thistle, found to be very prevalent in Buenos Aires and Palermo.
A glance at the map and we are not surprised to learn that there are two hay fever seasons in New South Wales, Australia. Its location at a latitude from 3o° to 4o° tells the story. A pollen slide survey at eleven stations in New South Wales indicates a prevalence of tree pollens in the summer months and grass plus plantain pollens during September, October, and November. For New Zealand, reports indicate that grass hay fever exists there as well as tree hay fever. Judging from its latitude, we are not surprised to learn that New Zealand has as high a grass pollen count as the southern part of Australia.
Information on hay fever conditions in Europe is sporadic. In general, there seems to be complete agreement that fall or ragweed hay fever does not occur in Europe.
In England, tree and grass pollens account for the bulk of hay fever cases. Many of the responsible trees and grasses are of the same species that cause trouble in the United States. Tree and grass hay fever is similarly known to be present in Scotland, Ireland, South Africa, India, Turkey, Russia, Germany, Spain, etc.
A detailed report on conditions in Palestine indicates a prevalence of hay fever due chiefly to Bermuda grass. A strange fact noted by the investigator, Dr. M. J. Gutman, is the widespread occurrence of a species of ragweed (Ambrosia maritime) which does not cause symptoms even among Americans who are sensitive to all the North American varieties of ragweed.
In China, as in Japan, there are many cases of asthma but hay fever seems not to occur. Nevertheless, many cases of pollen hay fever are seen among the Chinese and Japanese in America. An investigation of pollen conditions in Japan shows an absence of irritating tree or grass pollens. Ragweed which was formerly unknown there is said to be coming into the country.