Parasitic insects are organisms that live on or inside a host, deriving nutrients at the host's expense. Common examples include lice, fleas, and bed bugs. These insects often have specialized adaptations that allow them to attach to their hosts and feed on their blood or other bodily fluids. These insects can cause various health issues for their hosts, including irritation, allergic reactions, and the transmission of diseases. Control methods often involve maintaining hygiene, using insecticides, and employing preventive measures to reduce infestations in homes and on pets.