=Selecting the Pollen. The Skin Reaction.= The next step in the development of the pollen treatment was to substitute the skin reaction for the eye reaction in testing the patient's sensitiveness to various pollens. The advantage of the skin reaction over the eye reaction is that it permits testing many pollens at the same time and does not distress the patient as does a sharp eye reaction. While Noon and Freeman selected the one typical pollen of spring, the timothy grass pollen, and Koessler selected the typical fall pollen of the American hay fever, rag weed, for all cases of that season, later workers, using the skin reaction, go to the extreme of injecting the patient with each and every pollen to which his skin reacts. Oppenheimer and Gottlieb carry this individualization to the point of attempting to discriminate by the skin test the patient's varying resistance to his different pollens at each treatment. This resistance may rise for some and fall for other pollens so that six or eight different pollens in different doses must be injected separately at each treatment. This is individualizing the case with a vengeance and requires an expenditure of time and skill (I almost said _skin_) that must be rather expensive for the patient. A series of light scratches are made on the skin of the forearm or the inner side of the arm where the skin is delicate. The scratch must be only superficial and not draw blood. Really the best method is to make a round denuded spot by twirling a small brad-awl. A drop of extract of different pollens or a speck of the pure pollen protein is rubbed into each scratch and the result awaited for fifteen minutes. Within that time, a redness and swelling, like a hive or a bite, will appear at some of the scratches. This swelling is the skin reaction to that pollen. Its appearance indicates the presence in the skin of reaction bodies to that pollen. It is argued, and partially proved by practice, that the pollens to which the skin reacts are the pollens to which that patient has been sensitized and these pollens are selected for administration. =The Dose.= The first dose of pollen extract is the danger dose and differs for each patient according to his susceptibility for a given pollen. It is determined by dropping the pollen extract into the eye or rubbing it on the skin. To avoid anaphylactic shock, this dose must be incredibly small. Noon and Freeman's first dose was one-third c. c. of the weakest dilution of which one drop in the eye would cause hyperaemia. This was usually four drops of a millionfold dilution in water. Later doses were never more than 1 c. c. of a 1 to 100,000 dilution "to avoid unpleasant reactions." Goodale begins with five drops of that dilution that just fails to cause a skin reaction. Later, to avoid the risk of shock, he advises one-tenth of this dose.