Emotions modulate endocrinological and immunological responses. Negative emotions such as stress elevates blood glucose levels, while positive emotions such as laughter lessens the increase in postprandial blood glucose [1] [2]. In patients with atopic eczema/dermatitis syndrome (AEDS), symptoms are often exacerbated by stress and blunted hypothalamus-pituitary axis responsiveness to stress [3]. I have previously reported that stress enhances allergic skin wheal responses while laughter reduces those responses in AEDS patients [4] [5] [6]. Leptin is a protein secreted from adipocyte and is involved in regulation of energy metabolism and food intake [7]. However, leptin was also involved in stress responses and regulates hypothalamic-pituitary adrenal axis responses. Indeed, stress decreases plasma leptin levels in non-atopic subjects [8] [9]. Recently, one report also found leptin to be expressed in human mammary cells and breast milk [10]. These reports prompted me to study the effect of laughter on leptin levels in blood and breast milk in lactating AEDS patients.