PERHAPS in your mind the information on pollens given in the preceding chapter appears to be remote from your personal hay fever problem. You may be wondering about just how this information is to be applied. The answer is, that facts about pollens are intended to help you understand the workings of the hay fever plant world and how their activity is related to your hay fever.
While it is true that an understanding of pollens and plants is not necessary for obtaining relief from your hay fever symptoms, it is equally true that you will be equipped to obtain this relief more efficiently and effectively, as a result of this knowledge. The situation is analogous to the oft used example of the automobile driver and his understanding of the mechanism of the automobile. It is pointed out that thousands of people drive well, although they know little about the workings of their automobile.
With the advent of the war and the necessity to conserve rubber, gas, and metal, many agencies issued guides to drivers on how to handle their cars in a manner to best preserve these vital materials. In these chapters we intend to furnish you with a plant guide based on knowledge of pollens, to help you in preserving manpower against hay fever effects caused by plants that you might encounter.
THE FLOWERING PLANTS
The plants responsible for hay fever come under the large classification of flowering plants. This large class contains four groups, three of which are known to be associated with the causation of hay fever, namely, trees, grasses and weeds. The fourth is the wild flowers, which may on occasion produce hay fever symptoms but as a group are not important in the consideration of hay fever plants.
In variety and kinds there are over 150,000 different species of flowering plants. They are spread all over the world and in every kind of climate. They are found at the equator and at the Arctic Circle; at the top of mountains and at sea level. Some of the plants grow in water and some in the desert. In size, the flowering plants range from a quarter inch water plant to a 350 foot Eucalyptus tree. Fortunately only a small number of these plants are associated with causes of hay fever. But how are we to know which of these plants are important as a cause of hay fever? Obviously it would not be practical to collect pollens from the 150,000 species and test the results on human guinea pigs. Nor would it be feasible to collect the pollens from all the plants in your own locality and test you with them. An example of the impracticality of the latter procedure is the fact that within a radius of one hundred miles of New York City 268 kinds of grasses have been located. Add to this the probable number of different trees and weeds and you obtain well over 400 different species.
Since it is not advisable to test all the flowering plants, how then shall we know which ones to investigate as regards their hay fever producing potentialities?
THE NATURE OF HAY FEVER PLANTS
The answer to this question has been supplied by a formula consisting of the following five postulates pro-posed by August Thomen 1 for determining the relation of certain pollens to the causation of epidemic hay fever.
1. The pollen must contain an excitant of hay fever.
2. The pollen must be wind pollinated (anemophilous).
3. The pollen must be produced in sufficiently large quantities.
4. The pollen must be buoyant enough to be carried considerable distances.
5. The plant producing the pollen must be widely and abundantly distributed.
In order for a plant to be considered an important cause of hay fever it must satisfy the five conditions. But for our proposal of determining which plants to investigate in any new situation we would use the postulates in a different order. If the plant satisfied conditions 2 through 5 we would then consider it eligible for investigation by test with humans to determine whether or not it contains an excitant of hay fever. And we might add that up to the present time the only valid method of testing for the presence of the hay fever excitant, is to see if the pollen produces a hay fever reaction in a sensitive or allergic patient.
It must not be thought that the postulates represent idle theory. They have been applied and tested in actual situations and found to be admirably useful. However, these postulates do not apply to the pollens which cause hay fever in exceptional cases due to unusual contact, such as might occur in the case of farmers, fruit pickers, gardeners, florists, etc.
APPLYING THE POSTULATES
With regard to pine pollen, following the order suggested above, it is found to be wind pollinated, produced in large quantities, carried great distances, and widely distributed. But at least two investigators have reported that pine pollen is incapable of producing hay fever reactions by tests. Thus while pine pollen satisfies the four conditions sufficiently to warrant testing with humans, it is not a hay fever factor because it does not contain an excitant.
The second postulate of wind pollination rules out the insect pollinated plants as an important cause of hay fever. Such plants as the rose, goldenrod, dandelion, daisy, sun-flower, alfalfa and the fruit trees were once thought to be dominant in the cause of hay fever but are now known to be insignificant. As previously mentioned, the pollens of many of these plants cause positive reactions in tests but they are too heavy and sticky to be blown around in the air. Thus, though they may on occasion cause symptoms in an individual who for example walks into a field of goldenrod and disturbs the flowers, they are not responsible for the seasonal symptoms affecting hay fever sufferers.
The third postulate of producing pollens in large quantities, again rules out many of the insect pollinated plants. Due to the fact that these plants are insect pollinated they do not waste pollens like the wind pollinated plants and therefore do not produce many pollens. On the other hand this postulate confirms the reason for the ragweed plant being the foremost in the causation of hay fever. For not only is the plant widespread but it is estimated as producing the greatest amount of pollen of all the hay fever related plants.
According to the fourth postulate, the pollen must be buoyant. This buoyancy depends upon size, shape, weight and nature of the pollen. Though some plants are wind pollinated and produce dry pollens they are not important in connection with hay fever because the pollen is too large or too heavy to be buoyant. For example, a study of the grasses in Oklahoma City showed that Indian grass which produces a fair amount of pollen was rarely responsible for hay fever symptoms because its pollen grains are about twice the diameter of Bermuda grass which is the chief offender in this area.
The fifth postulate, that plants must be widely and abundantly distributed, helps to explain the absence of hay fever in many regions where hay fever plants do exist, For instance the writer has found ragweed plants in Bethlehem, New Hampshire; Eastport, Maine; Rangeley, Maine; Yarmouth, Nova Scotia; and a host of other places, in all of which localities, hay fever suffering due to rag-weed sensitivity is negligible or nonexistent. A major reason for the lack of hay fever in these areas is the sparse growth of the ragweed plant. With reference to this point Dr. Thomen cites the fact that there are plants in England such as Russian Thistle, lamb’s quarters, and wormwood, the same species of which, produce hay fever during August and September in the United States, but that individuals who are sensitive to the pollens from these plants are free from symptoms while in England during that period.
In general it may be said that the application of the five postulates is practical in most of the pollen studies conducted with hay fever plants. The results of a great many investigations show that in any given locality there are rarely more than ten to twenty plants that fulfill all the requirements. For this reason it is relatively easy for you, with the cooperation of your physician, to learn the appearance and facts of related importance about the plants responsible for your hay fever symptoms.