Most of us are fond of pleasant aromas. As I write I have my Christmas candle burning, creating the illusion I'm in a pine forest. Aromas that also top polls of people's favourite smells are vanilla, freshly baked bread, bacon and coffee.
Most of us also have a passing knowledge of aromatherapy - the idea that certain aromas can have therapeutic properties. When we inhale the scents of essential oils from plants and flowers, the theory goes, we feel beneficial psychological or physical effects.
Essential oils are having a bit of a moment on social media. You may have noticed some wellness bloggers and Instagrammers talking about and selling oils, in particular a prominent brand called Doterra, which sells in party-plan, multi-level marketing style.
You may also have noticed recipes featuring essential oils from these same sources. The oils are promoted for use in smoothies or to be added to water; in baking, dressings and savoury dishes as flavourings and for better health.
The use of these oils in food has prompted an investigation - and a warning - from Choice, the consumer advocate organisation in Australia. It recently published an article warning that essential oils can be dangerous when ingested. They quote the NSW Poisons Information Centre, which says essential oils should not be consumed; even in tiny amounts. Doing so can cause seizures, mucosal irritation, nausea, vomiting and burns, it says, and chronic exposure can potentially cause organ damage.
I asked Dr Adam Pomerleau, director of the National Poisons Centre here, for his advice.
"Different oils will have different specific health risks," he told me.
"Some can be quite harmful, and some products are highly concentrated, posing risks even with very small-volume exposures. Rather than self-diagnosing health problems and self-prescribing treatments, I would suggest that any health concerns are best discussed with a person's doctor for appropriate diagnosis and treatment advice."
And that seems to be the heart of the issue with Doterra and others like them. The people doing the selling are not doctors, typically, or medically qualified. Yet they're sometimes promoting the products as having specific therapeutic benefits.
This has caught Doterra out before. The company was formally warned in 2014 by the US FDA to reign in its sales force and stop its people making unfounded claims about the oils.
To date the evidence in general on the efficacy of essential oils to treat health conditions seems to be patchy. In terms of their safe use, the only people saying essential oils are appropriate for regular ingestion seem to be the people at Doterra, who do not appear to offer any warnings about possible harms.
I don't really know why you'd want to use basil oil in your dressing and not, say, actual fresh basil. After all whole plants contain lots of other beneficial properties besides their oils, which is why we're advised to eat lots of them.
If we like the fragrances of essential oils, that's grand. But it seems, according to the experts, we are definitely better off sniffing, not swallowing.
• Niki Bezzant is editor-at-large for Healthy Food Guide www.healthyfood.co.nz