Introduction: Nursing care takes place within nurse-patient relationships that can be demanding. In exceptional circumstances, the relationship may be destructive, and when this happens, significant onerous demands, appeals, or challenges can arise from patients and be placed upon nurses. Aim: The aim is to explore what can be termed boundaries of care responsibility when relationships with patients place significant destructive demands on nurses. Method: Based on a hermeneutical approach, this study introduces aspects of phenomenological philosophy as described by the Danish theologian and philosopher Knud E. Løgstrup and provides examples of nurses' experiences in everyday nursing practice drawn from a Norwegian empirical study focusing on remaining in everyday nursing practice. Data in that original study consisted of qualitative interviews and qualitative follow-up interviews with 13 nurses working in somatic and psychiatric health service. Discussion: The exploration of empirical examples demonstrates that nurses consider confronting demands from patients which manifest themselves as onerous and that they have to set limits to safeguard themselves. When the nurses had to manage acting out or actions from patients by opposing what was said and done, they experienced the situation as more than very unpleasant or connected to a perversion. Significant destructive caring relationships cannot be without boundaries, and explicating boundaries are of relevance to protect nurses from onerous demands. Protecting them implies reducing a hazard, that is, that nurses carry on even when this may be unhealthy for them. Conclusion: Consistently pinpointing boundaries between demands is assumed to be essential in caring relationships, as onerous or destructive demands are strongly connected to a content where boundlessness is involved. To protect both nurses and patients as valued human beings, thus raising and preserving the status of the nurse and the patient, the nature and possible detrimental effects of destructive caring relationships should be considered and examined.