Importance: Close social relationships are linked to improved individual health and even longevity. These effects are hypothesized to be mediated through improved neuroendocrine and immune functioning, particularly in individuals who engage in positive and affectionate interactions. Objective: To investigate the interacting effects of repeated intranasal oxytocin administration, a behavioral microintervention, and daily physical intimacy on neuroendocrine stress responses and dermatological wound healing. Design, Setting, and Participants: This randomized clinical trial was a double-blind, randomized, placebo-controlled study with laboratory visits and ecological momentary assessment. Interventions: Participants self-administered either oxytocin or placebo twice daily and engaged in structured positive interaction or not. Main Outcomes and Measures: Wound healing, cortisol, stress, and partner interaction were assessed. Results: Couples in the Partner Appreciation Task condition who received daily oxytocin showed improved wound healing, though effects were not consistently robust in sensitivity analyses. Oxytocin combined with daily affectionate touch and sexual activity was linked to reduced wound severity, and greater sexual activity was associated with reduced daily cortisol levels. Conclusions and Relevance: Intimate physical contact can reduce cortisol responses and, along with oxytocin administration, promote wound healing.
