What the Science Says About Peppermint Oil and Spiders

It’s Spider Season Again…

Ah Autumn. Cold foggy mornings, back to wearing layers again and the inevitable arrival of unwanted guests at Meadow Farm.

My girls are absolutely terrified of spiders, despite me churning out the usual “but they are the best fly catchers in the world” and “you are about a million percent bigger than a spider – it’s going to be much more scared of you than you are of it!” Neither of which seem to help at all!

Anyway, so far this autumn we’ve had some particularly enormous visitors and I’ve found myself stuffing my pockets with conkers on my morning walks with Cookie, as I heard years ago that conkers repel spiders and so I put them out religiously year after year.

Apparently, we’re not imagining the sudden influx either. Male house spiders become much more adventurous at this time of year as they wander around looking for females – unfortunately this wandering sometimes appears to involve galloping across our sitting-room floor. Or waving hello from the bath having miraculously negotiated the pipework on its latest mission.

But Do Conkers Actually Keep Spiders Away?

So, whilst filling bowls of conkers in the kitchen I thought I’d do some research as to where this talk about conkers came from. And whether there is actually any truth in it.

Sadly, this is where things become a little disappointing for my carefully collected conker stash.

The idea that conkers keep spiders away is a very well-established bit of folklore, but I couldn’t find any good scientific evidence showing that our ordinary horse-chestnut conkers repel spiders.

There is, however, a rather wonderful twist. I did find a scientific study looking at chestnuts and spiders – but the researchers weren’t testing our shiny horse-chestnut conkers at all. They used sweet chestnuts (Castanea sativa) – the edible kind we associate with roasting at Christmas. And, rather surprisingly, they found that these did deter some of the spiders they tested.

So somehow we have scientific evidence for the chestnut nobody puts on their windowsills, while the conkers I’ve been diligently collecting every morning remain decidedly in the folklore category!

So What About Essential Oils?

This, of course, got me thinking.

If spiders can detect and react to the natural volatile compounds released by plants, perhaps there might be essential oils that could make them have second thoughts about becoming our unwelcome house guests?

A quick Google search brings up all sorts of suggestions including peppermint, eucalyptus, cinnamon, citronella and clove.

But, as is so often the case with essential oils, there is quite a difference between something being endlessly repeated on the internet and something actually having some research behind it.

And this is where it gets interesting.

Peppermint: The Interesting One

Peppermint was included in that same 2018 study, and this time there really was an effect.

The researchers tested peppermint oil against three different species of spider. Two of the species showed a strong preference for moving away from the peppermint oil, although the third was much less bothered by it.

So we can’t say that peppermint oil magically repels every spider – spiders are far too diverse for that – but there is some genuine scientific evidence suggesting that peppermint oil can deter some species.

As an aromatherapist, this immediately caught my attention. Peppermint is an essential oil I use a lot when I want a blend to smell fresh, clear and uplifting. In fact, it’s an important part of my Revive & Revitalise blend for exactly that reason.

That doesn’t, incidentally, make Revive & Revitalise a spider repellent! It’s an aromatherapy blend, not a pest-control product. But I do love discovering that the same plant can have such completely different effects depending on who – or perhaps what – is smelling it.

Apparently Spiders Smell With Their Legs!

Now this was my favourite discovery during my research.

Spiders don’t have a nose like we do. Instead, they have an extraordinary collection of sensory organs on their bodies and legs which help them understand what is going on around them.

And recent research has shown that at least some spiders really can detect airborne chemical signals using tiny specialised sensory hairs on their legs.

So, in very simplified terms… spiders can smell with their legs! Although I have to say that knowing how sophisticated their legs are does not make me feel any more relaxed when eight of them suddenly appear from underneath the sofa.

Are There Other Essential Oils Spiders Don’t Like?

Peppermint isn’t the only essential oil scientists have looked at.

A more recent study tested ten different essential oils against a species of wolf spider. Five – catnip, cedarwood, cinnamon, citronella and clove – significantly deterred the spiders in the experiment.

Again, that doesn’t mean we can assume those oils will repel every type of spider. Different spider species can respond very differently and this is still an area where much more research is needed.

So… What Am I Going to Do With All These Conkers?

Well, I think the conkers are staying.

Partly because I have collected an awful lot of them and partly because they look rather lovely and autumnal sitting in bowls around the house.

But I shall no longer confidently tell my family that I am constructing a scientifically proven anti-spider defence system.

In reality, spiders are enormously useful creatures. They help control flies and other insects and are an important part of the ecosystem. I am therefore perfectly happy for them to continue their excellent work OUTSIDE in the garden.

A Final Word About Peppermint, Pets and Children

One important word of caution before everybody starts scattering peppermint oil around the house.

Essential oils are highly concentrated plant extracts and “natural” does not automatically mean harmless. I wouldn’t recommend leaving neat essential oils on cotton wool or in places where children or pets could touch, lick or swallow them. Always use essential oils appropriately and follow the safety guidance for the particular oil and method of use.

And if you have pets, remember that their physiology – and their sense of smell – can be very different from ours, so it is always worth checking whether an essential oil is appropriate around the animals who share your home. And always ensure that your pet is able to leave the room.

The same goes for my apparently useless-but-decorative conkers: horse-chestnut conkers can be harmful if eaten by dogs, so mine will be staying safely out of Cookie’s reach.

So my conclusion after disappearing down this particular autumn rabbit hole?

Conkers: lovely, traditional, but sadly not proven.

Peppermint oil: genuinely interesting evidence, but not a magic force field against every spider.

Spiders smelling with their legs: quite possibly my favourite fact of the week.

And the enormous spider that appeared in the kitchen last night? Still not welcome.