For decades, public health scientists assured us that the common cold was caused by our spending half the year indoors sneezing on each other. There’s no evidence, they told us, that Ireland’s long-standing position as the world’s leading producer of winter phlegm had anything to do with the cold or the wet. “Old wives’ tales” they said, when we pointed out that for 10,000 years our mammies have been telling us that we’ll catch our death if we go out dressed like that.
And then came a complete change of tack. Scientists at Yale actually looked at the evidence and found – surprise – that rhinoviruses, the culprits behind most colds and chest infections, thrive in cooler temperatures. And the lower the temperature, the lower our innate immune response to viruses. And what’s more, our noses are usually three to four degrees colder than the rest of the body.
The scientists’ advice for avoiding runny noses? “Always stay in warm tropical weather or try to prevent the nasal cavity experiencing very cold air.” Translated into Irish terms, that says “Emigrate south or dress the way your mother told you”.
The first lesson is that the phrase “There is no evidence” is just a euphemism for “We don’t know”, even when uttered by a scientist.
The second is that not all evidence is cast-iron scientific evidence. Most research advice will tell you to treat your family traditions with deep scepticism and most professional researchers will say “Yeah, right” (under their breath) when you tell them you’re descended from kings and princes. But even though centuries of tradition may not constitute forensic proof, it remains genuine evidence. Discount it at your peril.
But the most important lesson is that, although your Mammy might not be absolutely right absolutely all the time, the odds in her favour are pretty good.