In recent years, substantial medical progress has been made in improving children’s overall well-being, significantly reducing child mortality. One of the consequences of this has led to an increasing number of children living with chronic illness and/or long-standing functional disabilities, often involving numerous hospital visits, including extended stays [1]. Regardless of one’s age, being admitted to the hospital is frequently associated with much anxiety and, for some, an emotionally traumatic experience. Children are particularly vulnerable to the negative effects of being ill, but in combination with hospitalizations, this can result in heightened stress levels for both the child and their family [2]. For anyone, but especially for a child living with chronic disease, the long-term impact of chronic disease may eventually lead to fatigue, reduced mobility, and loss of bodily functions, placing the body under continuous duress [3]. In addition to experiencing stress caused by physical suffering from the disease, a child is exposed to other factors that negatively affect psychological well-being [4]. Examples of adverse factors include painful medical procedures, a foreign environment, feeling isolated, and not having their families close by. This has been confirmed to contribute to a child’s negative response to both the hospital stay and medical treatment [5].

Under stressful conditions, the child becomes more dependent on support from the family or relatives. A child’s coping mechanisms and emotional resources are not yet developed to manage the tremendous psychological and emotional stress they experience during a hospital stay [1]. Frequent or extended hospital stays are thought to negatively affect patients’ psychological state and increase the risk of long-term emotional and behavioral difficulties [6].

Complementary interventions such as clowns, music, film, and play therapy have become a major component of children’s healthcare today. These therapies are recognized as important factors in helping children in stressful hospital environments develop strong coping mechanisms. Game-like activities relieve anxiety but, above all, increase children’s ability to adapt. During play, the child can develop the ability to reason, think, and solve problems. Children who are good at playing also seem better at handling cognitively challenging situations. In addition, playing gives the child a sense of control over their life. However, seriously ill children are more likely to engage in repetitive, quiet, solitary play, which does not stimulate the abilities mentioned above in the same way [7].

Another type of complementary treatment that has become increasingly common is “animal-assisted therapy” (AAT), where the respective animal is often a specially trained dog [8]. Dr. Boris Levinson started the animal-assisted therapy movement. Levinson’s study indicated that adult patients became calmer when a dog was present at the sessions. Dr. Samuel Corson developed what he called pet-assisted therapy [9]. Most of the research on AAT has been carried out on the adult population, which has indicated that AAT therapy reduces pain, depression, and fatigue in patients with various types of medical conditions [10].

Although not as many trials have been conducted in the paediatric population on dog therapy, beneficial effects have been documented. In a 2006 study, a pre- and postoperative questionnaire was used to show a significant reduction in postoperative pain and anxiety in children between 5 and 17 years of age. Based on interviews after the intervention, the authors explained the results by the dog’s ability to distract the child from the pain or situation and act as a soothing agent [11]. Another study in 2009 compared pain ratings between two paediatric hospitalized groups. One group was given a 15–20-minute session with a dog, while the control group was assigned to rest in silence for the same time. The study showed that the children who were allowed to interact with a dog had a pain reduction that was four times greater than that of the children who rested in silence [12]. A study conducted in a paediatric oncology department in Canada noted that 89% of children who received AAT experienced an improvement in independence and appetite, a decrease in fear and pain, and positive effects on various psychological and psychiatric conditions [13]. However, it has not been possible to let a dog, now named Hospital Dog® (Definition see Fig. 1), work inside Swedish hospitals before scientific patient-safe guidelines were produced, of which this study is a part. This research has been necessary because of the strict guidelines in Sweden regarding health hygiene and allergen excretion, led to the development of the integrated medicine Hospital Dog® [14].

Definition of Hospital Dog®

Many studies have shown that hospitalized children are exposed to enormous stress due to both mental and physical strain. When humans respond to stress, the sympathetic nervous system is activated, leading to an increase in cardiac output and heart rate [15]. The locus coeruleus is centrally located in the pons of the brainstem and is involved in physiological responses such as attention, arousal, motivation, and cognitive function. During sympathetic activation, corticotrophin-releasing factor and vasopressin are released from the paraventricular nucleus (PVN). These two peptides also activate the hypothalamic-pituitary-adrenocortical axis (HPA), releasing adrenocorticotrophic hormone (ACTH) and stimulating cortisol secretion. Cortisol provides a constant energy supply for the body to deal with stress [16].

Oxytocin (OT) has many behavioural and physiological functions in the body, both centrally and peripherally [17]. Among other things, OT also includes nonpainful sensory stimuli such as skin-to-skin contact and warm bodily interaction [16].

Through the work of Kerstin Uvnäs-Moberg, it has been established that oxytocin lowers blood pressure, affects certain gastrointestinal hormones and spontaneous motor activity, increases the pain threshold, and reduces corticosterone secretion, which has a stress-relieving effect [16]. Stimulation of the alpha 2-adrenoceptor produces effects such as analgesia, anxiety reduction, sedation, hypotension, and a reduction in sympathetic activity [18].

Because many of the positive health benefits of Hospital Dog® overlap with those of oxytocin, one would expect that stimulating OT release would have similar medical benefits. Earlier studies have confirmed that adults experience elevated blood oxytocin concentrations after they have spent time interacting with a dog [19]. The aim of this study was to investigate variations in children’s OT levels by collecting urine samples from each subject before and after playing with a specially certified Hospital Dog®.