Some allergenic extracts produce erythema and wheal in intracutaneous testings. These reactions seem to bo induced by the entanglement of complicated determinant group of antigens and complicated reactive group of antibodies. We should perform hyposensitization therapy using the allergenic extracts which react to be the most positive and react to considerably low dilution test we should fail to treat the determinant group and reactive group causing allergic manifestations. When several kinds of allergenic extracts react mutually to the same degree by intracutaneous tests, we think they have common antigens, and so we have studied their frequency. The following are the percentages of the patients whose intradermal reaction was as strong as with House dust: 0.7% with Coryptomeria japonica, 3.3% with Poa pratehsis, 3.8% with Plantago lanceolata, 0.6% with Dactylis glomerata, 10.8% with Typha angustata, 5.2% with Paleum pratens, 8.5% with Festuca rubra, 5.4% with Ambrosia elatior, 7.5% with Miscanthus sinensis, 8.1% with Hormodendrum pedrosoi, and the average percentage of all the above was 6.5%. As for other common antigens, research is now being carried out.
