The paradoxical word 'cold' to label an essentially afebrile condition is found in various Indo-European languages to relate to words for death, birth, pregnancy, and sexual arousal. These in turn can be linked to primitive theories involving air as the carrier of the life principle introjected—or in the case of death, ejected—by respiration. Clinically, the appearance of colds while never excluding an infections factor, often follow loss or separation. Some colds conceal underlying depression, withdrawal of object libido, and conflicts over unconscious attempts to regain the lost object through oral and respiratory incorporation.