Do Essential Oils Pass the Smell Test?

Disclaimer alert: this article is here to share information, but more research needs to be done. So, don’t take this as medical advice. Talk things over with your vet when making decisions, and use your best judgment.

It’s a beautiful day. You and your dog are walking near a patch of grass when they stop dead, then sniff and keep sniffing. Gently, you tug on the lead, but – muzzle buried in the grass – they brace themselves and continue their nosework.

Scent is extremely important to dogs, much more so than to humans. All dogs have smart noses. In fact, MRI studies show that when a dog recognises the smell of a familiar human, the caudate nucleus in their brain lights up, signalling a happy event. For the average dog, a small pile of foliage contains a world of information. Though the canine brain is about one-tenth the size of a human brain, its smell centre is 40 times larger. We have roughly 5–6 million scent receptors, a fraction of the 125–300 million available to our canine companions.

For this reason, it’s necessary to proceed with caution when it comes to using essential oils around dogs. Because their senses of smell are much more acute than ours, several vets across the UK warn that essential oils could be toxic to your pets if accidentally ingested or inhaled in too large a quantity.

How the dog nose works

Their moist noses are cute, but there’s function behind that soft form. The mucus on a dog’s nose helps capture scent particles. When a dog’s nose is dry, they may lick it to improve reception. Dogs can also wiggle their nostrils independently, thereby detecting the direction of odours.

Despite the fact that the olfactory system is an ancient neurological pathway, we still do not completely understand how it works, either in ourselves or in our dogs. However, enough studies have shown it is critical to the survival of species across the animal kingdom – especially dogs.

How scents influence human behaviour

Though we may not understand it, most of us are aware that scent can influence behaviour. In the realm of human holistic treatments, the use of essential oils and herbal fragrances has become increasingly trendy and yoga teachers will sometimes use aromatic oils during classes.

Exposure to certain herbal or spice scents has been shown to have positive effects on humans. For example, Mark Moss and Lorraine Oliver, working at the Brain Performance and Nutrition Research Centre at Northumbria University in the UK, designed an experiment to investigate the pharmacology of 1,8-cineole, one of the main components of rosemary.

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After exposing 20 human subjects to varying levels of 1,8-cineole, the investigators tested their cognitive performance. Speed and accuracy test results showed that the concentration of 1,8-cineole in the blood was related to an individual’s cognitive performance: higher concentrations resulted in increased speed and accuracy. If scent can have positive effects on olfactory-challenged humans, it might be expected to have an even more pronounced effect on dogs.

How scents influence dog behaviour

While research on canines is limited, a study done at the University of Belfast explored the influence of four types of olfactory stimulation (lavender, chamomile, rosemary and peppermint) on the behaviour of 55 dogs housed in a rescue centre. The control condition used no odour other than those arising naturally from the dogs’ environment, (eg, odours from disinfectants and other animals). Using diffusions of essential oils and allowing two days between stimulants, the dogs were exposed to the scents four hours a day for five days.

According to the study, dogs exposed to lavender and chamomile spent more time resting and less time moving than with other olfactory stimuli used in the experiment. These odourants were also found to reduce barking and vocalisation in caged animals. On the other hand, fragrances such as rosemary and peppermint were found to encourage significantly more standing, moving, and vocalising.

How scent enrichment helps shelter dogs

Rescue centres are safe but sterile environments and recognising that as an issue, some have looked for ways to enrich those environments for their animals. With that in mind, an increasing number are introducing scents. For example, the Humane Society of Miami used a scent enrichment program, which incorporated essential oils such as lavender and vanilla.

McKamey Animal Center, located in Tennessee in the United States, is among the few that have worked with scent enrichment for several years, according to Morag Greaney, the centre’s former adoption and foster supervisor. According to Greaney, the scents – which include lavender, vanilla, and rosemary – are changed every day. The essential oil was mixed with water and then sprayed on the ground outside the dog kennels using nonaerosol methods. While there wasn’t an immediate reaction, staff observed that the animals tended to be calmer and more settled the following day. Greaney believes that it is not just a particular scent that makes a difference (although she does find that lavender has a calming effect), but the variety that helps stimulate the dogs’ brains.

The centre, which handles upwards of 200 animals, hosts a number of different breeds – Huskies, Labradors, German Shepherds, and Pit Bull-type dogs – among them. While the centre hasn’t conducted any formal studies to determine if different breeds are affected differently by the scents, its behaviour-assessment team uses lavender to help relax new animals prior to evaluation.

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The results of these small studies may be promising to help reduce the stress of shelter animals, but more research is needed on the safety of using essential oils more broadly with pets.

Should you use essential oils at home?

Scent enrichment, in tandem with other stress relief techniques, may work at home with guidance from your vet. “I would absolutely recommend that dog owners use scents with their animals,” says Greaney. However, she cautioned that people should first do some preliminary research and check with their vet to avoid any possible detrimental effects – that’s because many essential oils are toxic to pets. What may be safe for dogs can be fatal for cats and vice versa, while others are poisonous to both species.

Several vets across the UK warn that essential oils could be toxic to your pets if accidentally ingested or inhaled in too large a quantity – especially as their senses of smell are much more acute than ours. Ask your vet for more information. The Animal Poison Line also has a helpful list of toxic and non-toxic plants.