The increased presence of lithium "button" batteries in various household devices, such as cameras, remote controls, watches, hearing aids, and toys, has been associated with a rise in the rate of severe poisonings from battery ingestion among US children. The 20-millimeter lithium cell, which is about the size of a US nickel, appears to present the greatest danger to children because it can become lodged in the throat and burn the surrounding tissue. Experts say that because adults often do not witness the actual swallowing of these batteries and because such poisonings can be difficult to diagnose, prevention is of vital importance.