Acute stress increases resistance to infection. The alteration of this mechanism in chronically stressed people impairs the organism’s ability to mount a strong immune response with a resultant increase in morbidity. Acute stress induces a probable sympatho-adrenergically mediated increase in chemotaxis and adhesion molecules expression, thus promoting immune cells migration to sites of infection and/or inflammation, while chronic stress impairs this mechanism. Protracted stressful conditions decrease NK cytotoxic capacity. There is a substance P, which under stressful circumstances mediates the increase in macrophage cytokine production. Acute stress increases T cell mobilization through a β2-adrenergically mediated process, which is blunted during chronic stress. Psychological stress impairs the immune system’s ability to produce antibodies in response to a vaccine, thereby making the organism more vulnerable to infections.

We investigated whether inhalation of green odor (a mixture of equal amounts of trans-2-hexenal and cis-3-hexenol) prevents the skin-barrier disruption induced by chronic restraint stress in rats. To this end, transepidermal water loss (TEWL) was measured as an index of the disruption of skin-barrier function, whereas light- and electron-microscope examinations were performed to observe histological changes in the skin of the stressed animals. In addition, the effects on TEWL induced by chronic administration of a glucocorticoid, dexamethasone (DEX), were examined. Chronic restraint stress (8 h per day for 14 days) increased TEWL (vehicle + stress group). This effect (and the chronic stress–induced increase in adrenal weight) was prevented in rats that inhaled green odor at the beginning of each day’s restraint (2 h each day for 14 days; green odor + stress group). Electronmicroscope studies revealed that rats in the green odor + stress group possessed sufficient intercorneocyte lipids to create an effective skin barrier, although these had apparently been decreased in the vehicle + stress group. Daily administration of DEX for 14 days increased TEWL. The present results suggest that chronic stress–induced disruption of the skin barrier in rats can be reduced or prevented by green odor (possibly at least in part through an inhibitory effect on the stress-induced activation of the hypothalamo-pituitary-adrenocortical axis). Key words: adrenal gland, dexamethasone, hypothalamo-pituitary-adrenocortical axis, stratum corneum, transepidermal