Many old wives’ tales actually do have a basis in fact, and it’s not a good idea to dismiss them out of hand. For instance, it’s easy to dismiss your grandmother’s warning that you’ll catch a cold if you go out without a coat when it’s cold. The cold is caused by a virus, and viruses don’t work that way, says the modern scientific Westerner.

But Granny gets the last laugh: it has in fact been shown that large and rapid temperature changes sharply reduce the effectiveness of your body’s immune system, making it far more likely that you’ll become susceptible to one of the roughly three hundred strains of the coronavirus or rhinorvirus that cause the common cold, and that lurk almost everywhere when people are forced indoors by low temperatures.

You might well look askance at Granny’s advice, and with good reason at times — but ignore it at your peril.