The advice is age-old: make sure you don’t cool down too much, otherwise you will get sick! Stay out of drafts, don’t go outside without a coat, don’t linger in the cold, come back in quickly if you are sweaty or have been wet. And don’t go outside with wet hair. Is it sensible advice?
No, says Michael S. Kramer, professor of epidemiology and biostatistics at Canada’s McGill University in his book Believe it or not – The history, culture and science behind health beliefs and practices (2023). He even devotes an entire chapter to this, entitled ‘Dodging the Draft: Does Avoiding the Cold Reduce the Risk of Catching a Cold?’
‘Don’t go outside with wet hair’ is his favorite well-intentioned advice, Kramer writes. But he immediately refutes that: it is not the cold that makes you sick. They are viruses. The most common causes of colds are rhino, adeno and flu viruses, respiratory syncytial virus (RSV) and – yes – the coronavirus. You will therefore not become ill during or immediately after exposure to the cold. Unless you come into contact with infected people or their bodily fluids somewhere along the way.
English, German, Spanish and Greek
The linguistic connection between ‘cold’ and ‘catching a cold’ can be traced back at least to the sixteenth century, writes Kramer – long before there was any knowledge about pathogens. It is not only available in English and Dutch, but also in German, for example (Erkaltung), Spanish (resfriado) and Greek (kryo).
Kramer says that many people nowadays know that viruses are the culprit, but they think that infection alone is not enough to catch a cold. And, is cold really a necessary ingredient? Kramer delved deeply into the medical literature. Colds and flu symptoms often peak in the winter, when it is cold outside, he concludes. But that is not due to the cold itself, but to the fact that people spend more time indoors in winter. There is a clear link between infections and people sitting close together in heated, poorly ventilated spaces.
But what about our immune system? Doesn’t that become more vulnerable if we have to put more energy into warming ourselves? Some lab studies in mice seem to suggest this, Kramer notes, but the few human studies provide inconclusive results.
Cold plunge pools
A search in the PubMed database confirms this. “The issue remains subject to debate,” said a 2022 review of cold plunge pools. There are indications that cold exposure activates certain immune cells, but the question remains whether this has a clinical effect. An older review, from 2002, concludes that in any case, “there is no evidence that cold exposure suppresses the immune system.”
But then: a major 2019 study revealed a new, direct defense mechanism in the nose. After contact with intruders, the nasal mucosa secretes small blisters containing substances that kill pathogens. And now it comes: at the end of 2022 it turned out that this system works less well in cold air.
Kramer’s book may already have been at the printer at the time – or he may not have found the news so relevant in this context. After all, you contract most infections indoors. In any case, anyone who is fit and avoids sniffles can safely go outside with wet hair.
To share
Email the editor
