Like Powis with her onions, parents and grandparents pass down advice to the next generation.
And as Morice explains, there is a genetic reason why certain treatments become family favourites.
“The thing with all these agents and remedies is that different individuals respond differently to them,” he says.
“This tendency to cough and have relief of cough from certain remedies is inherited.
“So, if there’s a family lore that says ‘we use menthol and it works very well’, then it’s probable that children in the family will also respond to the same menthol lozenge or inhaler.”
So why do placebos also work for some people?
“Normally, coughing is held with the brakes on by the brain,” Morice says.
“In some people, if you stimulate these brakes, you reduce the coughing. It’s not just them imagining it – it is a demonstrable, neurological nerve effect from the brain controlling the cough.”
So could this be why Deborah knows her onions work for her?
Morice says it is possible there is “a germ of truth” in this remedy and that the smell has an impact.
“Perhaps they have found in her family, it alters their perception of the cough.”
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