The traditional folk theory is that a cold can be "caught" by prolonged exposure to cold weather such as rain or winter conditions, which is where the disease got its name.[86] Common colds are seasonal in temperate latitudes, with more occurring during winter. The experimental evidence for this effect is uneven: many experiments have failed to produce evidence that short-term exposure to cold weather or direct chilling increases susceptibility to infection, implying that the seasonal variation is instead due to a change in behaviors such as increased time spent indoors at close proximity to others.[9][21] However, other experiments do find such an effect for both body chilling and cold air exposure, and a number of mechanisms by which lower temperatures could compromise the immune system have been suggested,[17] while other experiments have shown that exposure to cold temperatures may instead stimulate the immune system.]作者: jw0310 时间: 2011-12-12 23:38:23