Rejection is when your body treats your jewelry as an irritant and decides to push it out of your body, or “reject” it. (This is the same way your body deals with a splinter or glass shard embedded in the skin.) With anchors, one of the warning signs of rejection is a thinning of the tissue around the post—i.e., the skin becomes red and shiny as the anchor begins to move toward the skin’s surface. Another sign is when the anchor starts to sit at an angle; in late stages, the base of the anchor will actually become visible, even to the point of the foot poking up through the skin. Once the anchor starts to reject, it should be removed promptly to minimize scarring.
Be aware that surface anchors can reject anytime, even after they are fully healed, and often some sort of trauma (like snagging them) will start this process. So be mindful, and baby your anchor as much as possible.