More scientific weight to what seems intuitive: Massage increases oxytocin.
According to the New York Times, reporting on research at Cedars-Sinai:
Volunteers who received Swedish massage experienced significant decreases in levels of the stress hormone cortisol in blood and saliva, and in arginine vasopressin, a hormone that can lead to increases in cortisol. They also had increases in the number of lymphocytes, white blood cells that are part of the immune system.
Volunteers who had the light massage experienced greater increases in oxytocin, a hormone associated with contentment, than the Swedish massage group, and bigger decreases in adrenal corticotropin hormone, which stimulates the adrenal glands to release cortisol.