Symptoms are at the heart of nursing care.Much of what nurses do for and with patients is focused on symptoms: measuring them, assessing factors that may inuence changes, developing prevention and management strategies, and helping patients with ongoing monitoring and self-management.e eory of Unpleasant Symptoms (TOUS) was developed to highlight important aspects of the symptom experience in order to improve understanding and help guide nursing research and practice.It is exciting that interest in the theory and its application has been increasing internationally.e TOUS has three major related parts: the symptom(s), factors that inuence the symptom (inuencing factors), and the performance outcome.e theory denes symptoms subjectively, as perceived by the patient.Symptoms are proposed to vary in intensity, timing (e.g., time of onset, duration), the distress that the patient experiences, and quality (how they feel).Two or more symptoms can occur together, a phenomenon currently identied as a symptom cluster.Multiple symptoms occurring together may have the same or different causes, and can have cumulative or multiplicative effects.By categorizing inuencing factors as physiological, psychological, and situational, the TOUS encourages thinking beyond the physical realm of care.Physiological factors include age, gender, and variables related to the illness(es) and treatments.Psychological factors include mood and cognition (for example, knowledge about and understanding of the illness).ey exert strong inuence on symptoms.Situational factors are external to the individual.ey emphasize the potential impact of the physical and social environments on the patient.e outcome of the symptom experience is performance, which is dened broadly to include physical, cognitive, and social role performance (1,2).e TOUS emphasizes the complexity of symptoms, while also implying possible preventive and management strategies.According to the theory, the three related categories of inuencing factors affect the occurrence of one or more symptoms and how they are experienced.e symptom(s), in turn, affects the individual's performance, which can feed back to inuence the symptom experience and the inuencing factors.e theory does not include explicit interventions.Instead, it is assumed that many of the components and relationships in the TOUS could be targeted for intervention.Several studies have applied the TOUS in practice with positive results.It should be noted that these applications have had multiple components, and all include teaching of the patient and family caregivers.Some of the practice applications that would be consistent with the theory include the following.