He suggests Oscar is able - like dogs, which can reportedly smell cancer - to detect ketones, the distinctly-odoured biochemicals given off by dying cells.

Chemicals in this group, such as acrylamide and methylvinyl ketone, also show up in car exhaust, cigarette smoke, industrial settings, even French fries.

Ketosis occurs when you don't have enough sugar (glucose) for energy, so your body breaks down stored fat, causing ketones to build up in your body.

She points to a 2004 study, for example, in which she and colleagues found no evidence that humans could discriminate between acetophenone and deuterated acetophenone.