Hay Fever - Specific Therapy
( Originally Published 1943 )
A person with mild hay fever may be able to get along quite well with some of the mechanical devices just cited.
But if his hay fever is at all severe, and if he is unable to obtain complete avoidance by going to a resort, he should be immunized. Most people come under this classification.
It was Dr. Noon of London who first successfully immunized a human being to a pollen. He did it by injecting under the skin very minute amounts of an extract of the offending pollen and in successive injections gradually increasing the dose. This is the same method used today, but in the thirty odd years since Noon's time many refinements of technique have been made which make the out-come much more certain of success. However, even today there are failures and it is the exceptional rather than the usual case that obtains one hundred per cent relief. In most cases, though, the results are so good that the patients are well satisfied.
DIAGNOSIS BY SKIN TESTING
Before undertaking treatment, it is necessary to test the patient with extracts of many pollens to determine which ones are actually causes of trouble. From the history of the case, and a knowledge of the plants in the patient's neighborhood, the number of possible offenders can be greatly limited and the number of tests kept down to a reasonable figure. The scratch method of testing is still the one most frequently used, though allergists do not usually consider it the best. An area of skin on the forearm or back is cleaned with alcohol and a short shallow scratch, not deep enough to draw blood, is made on it. A strong extract of the suspected allergen is then placed on the scratch and allowed to stand in contact with it. If the individual is sensitive, an itching wheal, similar to a hive and surrounded by an area of redness, will appear in five to fifteen minutes. A much more sensitive and accurate method is the intracutaneous test. In this a minute amount of a rather weak extract is injected by hypodermic syringe into the uppermost layers of the skin. In the sensitive patient a wheal soon forms as in the scratch test. The intracutaneous test has the advantage of indicating much more clearly than the scratch test how sensitive the patient is, as well as the particular substance to which he is sensitive. This added information tells the doctor the approximate dosage that will be required to obtain satisfactory results. While the older scratch test is still used more than the intracutaneous by the medical profession at large, most allergists today rely on the intracutaneous test to make their diagnoses.
MAKING OF EXTRACTS
The same extracts are used in testing as in treating. Hay fever is caused by those portions of the pollen that are soluble in water. There are other portions that are fatty and are soluble in ether or carbon tetrachloride (cleaning fluid); these occasionally cause skin diseases, especially of the hands and arms of people who are working around plants. If the oily portions of the pollen are injected with the water soluble parts, there is a possibility of causing untoward skin reactions. For this and other reasons, in making an extract, it is customary first to remove the fat from the pollen with ether. When the ether has dried, the pollen is soaked a few hours in an extracting fluid. There are many of these, the commonest being a slightly alkaline salt solution and a solution containing as well about fifty per cent glycerine. The pollen is then filtered out, leaving a clear yellow or brown liquid. Since this liquid is to be injected into people, it must be sterilized or infections might result. Heat, which is used to sterilize most things, destroys the active ingredients of an extract and can not be used. It must therefore be sterilized by a cold method Berkfeld or Seitz filtration. This is just the same as putting it through a sieve, except that the spaces in the Berkfeld and Seitz filters are so tiny that bacteria cannot go through them.
STANDARDIZATION OF EXTRACTS
Having made the extract, it must be standardized if dosage is to be regulated carefully. The old method, still used to some extent, merely expresses the ratio between the weight of pollen and the extracting fluid used. Thus, if five grains of pollen is extracted by one hundred grams of extracting fluid, the resulting extract is called a 5% or 1-2o (one to twenty) extract. This is a strong extract and is diluted down for use to 1-loo, 1-1000, 1-10,000, etc.
It appears at first glance that this is a logical and perfectly satisfactory method. However, it has been shown that pollens from different localities and in different years in the same locality will vary in their activity and content of antigen as much as a hundred per cent. Various methods have had to be worked out to take this into account if consistent results are to be obtained from year to year. It has been found that the activity of an extract fairly closely follows the amount of protein in it and that the nitrogen content of the extract is an indication of the amount of this protein. Most extracts today are therefore standardized by either measuring the total amount of nitrogen in them or else by precipitating the protein out of the extract and measuring the nitrogen in that. Such methods of standardization will give comparable results with different batches of extract, but are responsible for inserting one element of confusion into the picture. If. standardized by the protein nitrogen method, the extract is labeled in units, one unit being defined as 0.00001 milligram (one one hundred millionth of a gram or 10-8 gram) of protein nitrogen. An extract is said to be a 100 unit extract if it contains 100 units in each cubic centimeter. Thus a 10,000 unit extract is a strong extract, whereas in the old method, a 1-10,000 extract is weak. This is not a serious state of affairs, but it has resulted in accidents of overdosage.
People vary widely in their degree of sensitivity. But the severity of their symptoms is not necessarily proportional to the degree of their skin reactivity on test. A person may be extremely sensitive on test and still not have very severe symptoms of hay fever, while another may be relatively insensitive on test and have very severe symptoms. The test, then, really shows us not how bad the symptoms are, but how much extract to use in treatment. Not infrequently a person will be found on test to be sensitive to a pollen and still have no symptoms of hay fever. This does not mean that the test is no good. The individual is sensitive. It means that this person has not yet had enough exposure to the pollen to give him symptoms but that there is a strong likelihood that some day he will have enough contact with it to produce hay fever. It is important to correlate the history with the findings of the tests if a correct diagnosis is to be made. One often hears of the opposite state of affairs. A person, for instance, has hay fever during the ragweed season but gives negative skin tests to ragweed. Many such patients are given injections of ragweed for several years without benefit, in the mistaken belief that they will be improved if enough extract is pumped into them. Persons reported to be sensitive to a pollen but not giving a skin reaction are mythical. Such people are sensitive to something else, like the tomato patient described in a previous chapter, but we are not always smart enough to find out what it is.
This subject of the degree of sensitivity of different people brings up a seemingly paradoxical situation. On first thought, it would be expected that the more sensitive a person is, the more extract would be required to immunize him. The opposite is true. A very sensitive patient can not tolerate large doses of extract, and no matter how many injections are given, a point is reached beyond which he can not be forced. This dose may seem surprisingly low, but he will get just as good results as the relatively insensitive person who requires much larger doses. Thus, a very sensitive patient may require a top dose of only 500 protein nitrogen units, while the relatively insensitive may require 30,000 protein nitrogen units. It should be evident from this that the treatment of hay fever is a highly individual matter and that it is impossible to follow any set scheme of treatment that will apply to all cases.
To immunize a patient successfully, the doctor must know what pollens are responsible and how sensitive the patient is to them. It is not necessary, however, to immunize to all the different pollens which give skin reactions. We know that the pollens of several plants are antigenically the same. For example, a person who gives a positive skin reaction to sweet vernal grass will always give positive skin reactions to red top and timothy. A person sensitive to short ragweed is always sensitive to giant ragweed. However, a person sensitive to grass is not always sensitive to sorrel or plantain, and a ragweed patient is not necessarily sensitive to cocklebur or lamb's quarters. Much time is wasted today in testing for several grasses and ragweeds. It is only necessary to test for one and treat for one.