In the past decade, skin testing (scratch and intradermal) with various substances has come to play an important rôle in the determination of etiologic factors of bronchial asthma and allied conditions. The information derived from testing the patient himself, known as the "direct method" of skin testing, has brought about a rational method of treatment for allergic conditions. However, the testing of infants with asthma, and especially those with dermatoses such as eczema and urticaria, presents many difficulties. Prausnitz and Küstner1 first demonstrated that when blood serum of a patient sensitive to a protein is injected intradermally into the skin of a normal person, the area in which the injection is made becomes locally sensitized to the specific protein. Local passive transfer of hypersensitiveness into normal human beings was verified by de Besche,2 Coca and Grove3 and others. The specific reacting substance in the blood of a