So, I concluded long ago that there must be two kinds of hay fever, one kind curable by diet, bathing and exercise and another kind in which habits of living and eating made no difference; and I had seen mostly the other kind.
Now, there may well be cases of hay fever as there are known to be cases of that other anaphylaxis, asthma, that are pure examples of food anaphylaxis. In such a case, detecting the irritating food and removing it from the diet is the proper path to cure. The error in our former practice was to divide foods into good and bad for certain diseases. We should rather think of foods as good or bad for a particular patient.
The plain people long ago crystallized their experience in diet in the maxim that what is one man's meat is another man's poison, but your scientist will never believe anything until he sees it in a test-tube and physicians have kept on a few centuries behind the rest of the world prescribing diet for all cases of the same disease irrespective of whether or not it agreed with the patient. Witness the rigid diets for tuberculosis and Bright's disease. So, inevitably, there had to be a diet for hay fever and equally inevitably, the same diet did not agree with everybody.
Scientific men are fond of stating in scientific terms what everybody else knows already. While we have known for a long time that some foods did not agree with everybody, science is just now demonstrating that one man's meat is literally another man's poison by testing the different food proteins on the skin and calling the condition food anaphylaxis or food allergie.
As the patient reader of the chapter on Pollens will remember, the anaphylaxis or sensitiveness of the patient to particular pollens is tested by rubbing a speck of different pollens into scratches on the skin. This skin reaction as a test of anaphylaxis was used by Schloss with different foods before it was adopted in hay fever; and it has been taken up by the dermatologist also. The dermatologist has long suspected that certain skin diseases, as urticaria, and eczema, are aggravated or produced by certain foods but he has been unable to demonstrate just what foods were at fault. The problem was confused by the fact that he had found no guiding principle. Food that one patient could eat with impunity brought out a beautiful eczema or urticaria on another patient. The uric acid theory was one effort to solve this problem but it was not comprehensive enough and it was not true. Forbidding nitrogenous foods has been a favorite formula with some and they straightway advised milk, which is highly nitrogenous. The recent recognition that food sensitiveness is an anaphylaxis and the detection of the foods at fault by the skin reaction may supply the missing guiding principle that was needed to adjust a diet to the individual needs.
The poisonous element in food is the protein. The food itself will serve for the skin test but it is better to use the pure food protein, which gives clearer reactions and avoids contamination. Proteins of all our common foods are now obtainable in the drug trade put up in tiny capsules ready for the test.
The skin is cleansed with soap and water and dried. A number of little spots are denuded of their superficial epithelia by twirling a small brad-awl, which should not scrape deeply enough to draw blood. Most workers speak of scratching the skin but the brad-awl scrapes to the proper depth more quickly and easily. The spots are marked with the names of the foods to be tested, as milk, beef, potato, oats, etc., and a drop of a five per cent solution in water of the respective proteins is rubbed into the spots. One spot is left as a control, into which normal saline or 3% solution of milk sugar is rubbed, as the proteins of commerce are made up with milk sugar. Within five or ten minutes, there appears a redness and swelling, as with the pollens. As with the pollens, a patient who at any time has been poisoned or, as we now say, sensitized by any of these foods, still has circulating in his blood or fixed in his skin the reactive bodies to that food. These reaction bodies react to that food on the skin by redness and swelling. Food proteins that cause no redness and swelling are thought harmless for that patient. Foods that cause the reaction are thought to be those to which the patient has been sensitized and to which he has not developed or maintained an efficient defence. There is a contradiction here; for the reaction merely shows the presence of defense bodies in the blood and does not tell us whether that defence is or is not efficient. However, even if the argument limps, the results reported are encouraging. Some striking cures have been reported by simply excluding these foods from the diet. The test is simple and harmless if the scratch is not too deep and if the protein is not injected beneath the skin. If injected beneath the skin or rubbed into a deep scratch, the food proteins, like the pollen proteins, may be dangerous. If they are absorbed rapidly into the circulation of a patient who happens to have been sensitized to any of them, there is serious danger of anaphylactic shock.
If these observations prove reliable, here is a method of selecting a diet for the individual patient that surpasses in accuracy anything that we have ever known. If hay fever is ever a food anaphylaxis, this method of testing the food sensitiveness of the individual patient promises much; but these observations are still too new and unconfirmed and the skin reaction too uncertain to rely on it implicitly yet. There was a time, back in 1908 to 1910, when the skin reaction for tuberculosis too was highly valued. Enthusiasts proposed to test all the school children and all the soldiers and all the factory workers and segregate the tubercular by the skin test. The diagnosis of tuberculosis was to be put in words of one syllable.
That dream is over. Tuberculin skin reactions have now been made by the million and we know that a positive reaction means nothing but that, at some time, the patient has been infected with tuberculosis. The skin test does not tell us whether he has recovered long ago and built up a good defense or whether he is still sick with tuberculosis and will die of it. It reacts equally well in the healthy, vigorous subject who at one time has had a mild tuberculosis and recovered, in the patient with early phthisis and in the advanced case. In Kraus and Levaditi's Handbuch der Technik und Methodik der Immunitätslehre, 1911, page 205, von Pirquet himself, the grandfather of all the skin tests, says, "A positive skin reaction indicates with certainty that the organism has been infected with tuberculosis. Of the localization, extent and prognosis of tubercular infection, a positive skin reaction gives no conclusion." Yet hundreds of physicians to-day are making diagnoses of tuberculosis by the skin test; for if there is one thing more difficult than to get a new idea into a doctor's head, it is getting it out again when the idea proves fallacious. So, I view these skin reactions for food and pollens with some suspicion of their real value in diagnosis and prognosis and as guides to treatment. Still, Talbot says, "Experience has shown that when a positive skin test is obtained for a food and that food is then excluded from the diet, the general condition of the patient almost invariably improves and in many instances a cure results." May his words prove true.