Bed bugs are small parasitic insects that feed on the blood of mammals and birds. Bed bugs live in mattresses, linens, and headboards, as well as in the walls, flooring, and other furniture in areas where people sleep in homes, hotels, and other dwellings. Because bed bugs usually feed at night when people are sleeping, most people do not realize they were bitten. The only evidence that a person was bitten may be itchy welts that appear a few days later. Bed bugs do not transmit disease, but are a nuisance and infestations should be controlled by a licensed pest control operator.