AbstractMost patients have no response to injectable collagen or silicone, but some cases may have positive or ‘undersea’(= clinically negative but immunologically positive) response to collagen. From the results of the Macrophage migration inhibition test, the relative immunogenicity was augmented most when we used implants with the following combination. The firstimmunization was collagen and the second one was collagen with silicone.The augmented antigenicity might be enough to cause an allergic reaction to the patients who had no response to each implant alone. The purpose of this article is to warn of the potential hazard of injection.