Skin Reactions to Pollen and to Histamine.

Certain “allergic” patients are classed as non-sensitive because no skin reactions are obtained when they are tested with the usual allergens. It is important to know if a direct relationship exists between reaction capacity and the type of skin under study, or if the site of the test is an important factor. The work of Lewis 1 and his associates has furnished us a method for studying reaction capacity in the skin hypersensitive or non-sensitive individual.

Histamine, in the following dilutions, 1-1,000; 1-10,000; and 1-100,000 (of the base) was employed as a test substance for both types of patients. Similar dilutions of pollen extracts were tested on those who were pollen sensitive. All tests were intracutaneous, and were made in the long axis on the flexor surface of the forearm. The amount injected, usually 0.01 cc., produced a welt 1.0 to 1.5 mm. in diameter. Beginning at the antecubital space the first welt was made with the 1-1,000 dilution of the test substance. The 1-100,000 was the most distal. At the wrist the opposite margin of the arm was employed and the tests were in the reverse order—the 1-1,000 was most distal. The tests were repeated 3 times using alternate arms. The wheal, the area of “reflex arteriolar dilatation”, 1 —secondary erythema—was measured and the presence of pseudopods noted. The patients included some with an elastic and others with a senile or crepe-paper type of skin. Some were taking epinephrin frequently, others had never employed the drug.

The senile, atrophic, “crepe-paper” type of skin may give as large a reaction to histamine, or to pollen if the patient is sensitive, as is given by an elastic skin. The variation from patient to patient is characteristic of the individual and seemed to be unrelated to the type of skin.