# The Encyclopedia Americana (1920)/Hay fever

Edition of 1920. See also Allergic rhinitis on Wikipedia, and the disclaimer.
HAY FEVER, a nervous affection of the mucous membranes of the eyes, nose, mouth, pharynx, larynx, and bronchi, characterized by a profuse flow of secretion from the nose, and of tears from the eyes, and accompanied in some eases by asthma. It is induced by the lodgment on the mucous membranes of the eye, nose and throat of the wind-borne pollen of certain plants. The disease varies in its severity according to certain atmospheric conditions and the amount of pollen in the air. Occurring at the haying season the disease received its title through that association. The prevalence of
catarrhal symptoms in summer separates it from an ordinary “cold in the head”; while their combination with difficulty of breathing prevents it being mistaken for spasmodic asthma, in which there is seldom any catarrh. There are three combining causes of this affection, which is largely nervous: First, a predisposing cause in some nervous disease, with a probable lesion in the fourth ventricle of the brain. Second, deformity, such as a deviating septum, in the nasal region. Third, inhalation of a special pollen. Removal to the seashore or the mountains is beneficial in most cases, and a sea voyage, or other complete removal from pollen afflicted regions brings entire release. The succinimide of mercury affords relief in many cases, and arsenic, iodides, bromides, and other nerve specifics benefit others. For the asthma, iodide of potash, 5 grains with 5 minims of tincture of belladonna in syrup of orange-peel should be taken every two hours. Calcium chloride is also very effective where asthmatic symptoms are marked. Inhalations of nitre-paper, stramonium leaves, etc., with wine of coca internally, are also useful.
These remedies are, however, merely palliatives, and scientific men have been for some time making investigations which may eventually lead to the discovery of a radical cure.
Professor Dunbar, of Hamburg, who has been studying the subject for seven years, is one of those who hold out the hope for curing hay fever by a rational treatment.
According to him, the disease is caused by the pollen of grasses, but not by mechanical irritation. He has extracted from the pollen a protein poison, or toxin, which is insoluble in ether and alcohol, but soluble in water and weak saline solutions, tears, the mucus of the nose and the serum of blood. A solution of this toxin dropped into the eye or nose at once produces the characteristic symptoms of hay fever. The same symptoms in an aggravated form occur when the solution is injected hypodermically.
This discovery suggested treatment by the serum method and Dr. Dunbar set to work to produce a curative serum by inoculating animals with pollen toxin, and a serum was eventually obtained which, when dropped into the eye or nose together with pollen toxin, completely prevented the attack which the latter alone would have caused. In practical use, however, both the serum and the vaccination treatments have failed, and it is now generally admitted that the only completely effective treatment is avoidance of the cause.
Recent investigations have established the fact that hay fever is a distinctly preventable disease. Where there is none of the poisonous pollen the disease does not exist. The fact of prime importance is that only wind-borne pollen produces the disease. The pollen of golden rod, daisies, dandelions, and sunflowers will produce the symptoms if directly inhaled, but at a little distance such plants are harmless: their pollen is too heavy to be carried by the wind. On the other hand it has been found that some pollen travels several miles on the wind, but the farther it goes the more widely it is scattered, and it is rarely in sufficient quantity to produce the disease beyond half a mile from its source. Another established fact of importance is that immunity from the
disease does not imply that the immune person is not inhaling pollen, but simply that he is not inhaling more than his system can resist. It is only when the pernicious toxin of the pollen is assimilated beyond the capacity of resistance that the symptoms appear. After an attack is definitely begun, a much smaller addition of the toxin is sufficient to keep it going. The very wide degree of personal resistance to the pollen toxin explains the susceptibility of some persons and the immunity of others breathing the same pollen and in the same quantities. Unfortunately an attack of the disease leaves the patient more susceptible than before. Curiously, however, farm workers who are continually breathing pollen do not have hay fever.
The earlier summer cases of hay fever are attributed to the pollen of several of the grasses and to that of the yellow dock (rumex crispus). The midsummer cases are said to be due to “careless weed” (amaranthus spinosus) and cocklebur (xanthium Canadense). The much larger proportion of cases of the early autumn are unquestionably due to the pollen of the ragweeds ambrosia trifida and ambrosia elatior. The marsh elder (iva ciliata) is also credited with a share in the scourge. The official experiment of cutting the ragweeds in and about New Orleans in the summer of 1915 resulted in shortening the “season” of hay fever in that city by several weeks. The output of pollen was so reduced within a half-mile distance from the city as to render it innocuous except to the most susceptible, and these eventually escaped by temporary removal to the centre of the city, beyond the reach of the pollen-laden winds.