SmellAbility is an assortment of tools to support people with a smell disorder.
It includes testing current smell ability, smell training guidance, and some FAQ’s. We will be continually reviewing, improving and increasing the resources available to support self-help.
The Theory and Some Science:
The idea that our sense of smell can be improved via training might at first seem strange, but the more you think about it the more it makes sense. Going to the gym and lifting weights can improve muscle mass and tone, and practising the guitar regularly will (hopefully!) improve proficiency. So will spending time sniffing odours therefore improve one’s ability to detect them?
Prof Thomas Hummel’s 2009 study
In 2009 Professor Thomas Hummel, who runs the Smell and Taste Clinic at the University of Dresden in Germany, ran a study to investigate whether repeated short-term exposure to odours over a twelve week period would have any effect on the olfactory ability of a group of anosmia sufferers. An abstract of Prof. Hummel’s paper can be viewed here.
The study involved two groups of people with anosmia, all of whom had lost their sense of smell through either head trauma, severe infection of the upper respiratory tract, or for reasons unknown (idiopathic). One group was given four essential oils – rose, eucalyptus, clove, lemon – and told to sniff each one every day, morning and evening, for ten seconds at a time over a period of twelve weeks. The other group did not participate in the olfactory training. Both groups were tested at the beginning and then at the end of the twelve week period using sniffin’ sticks. What Prof. Hummel found was that a number of patients who had undergone the training (30% of the test group) experienced some improvement in olfactory function, compared to the group who had not participated. Improvement occurred in patients who had suffered smell loss due to upper respiratory tract infection, head trauma and idiopathic olfactory loss.
Plailly and Royet’s 2011 Study:
In 2011 researchers Jane Plailly and Jean-Pierre Royet demonstrated that similar areas of the brain are stimulated when both detecting and imagining particular scents.
Their subjects were both professional perfumers and students from ISIPCA, a college in France that trains perfumers. Individuals were placed in an MRI scanner and asked to imagine the smell of a particular substance, the name of which appeared on a screen in front of them.
They found that the level of activity in the brain actually decreases with the experience of the person being tested – essentially, the brains of more experienced, expert perfumers have to work less hard to imagine particular odours due to the training that they have undertaken.
The fragrance industry is, of course, dependent on the sense of smell and fragrances are developed by ‘trained smellers’, aka perfumers, who spend years smelling and learning the scents of a huge variety of fragrance ingredients.
2015 study: ‘Modified Olfactory Training’
In 2015 a further study was published which showed that smell training is potentially beneficial for people with impaired sense of smell due to a previous upper respiratory tract infection, and that some additional benefit can be gained from using a wider range of odours over a longer period than the 12 weeks used in earlier studies.
The work was done at the Istanbul Surgery Hospital by a team including Professor Thomas Hummel and was reported in the Laryngoscope journal.
You can read a summary of the paper published in the Laryngoscope journal here.
What Does This Mean For Someone With A Smell Disorder?
The results of the various research studies does give some hope for people affected by olfactory loss. We’ve been in touch with Fifth Sense members who have had success with smell training, sometimes alongside a clinical intervention. In many cases the training has, potentially, helped people to detect other scents in their environment, rather than just the scented oils used in the training.
There are lots of unknowns, however there is no evidence to show that smell training alone can bring about recovery of the sense of smell. Perhaps the best way to think of it is as an aid to olfactory ability.
It is thought that smell training may help the regeneration of the olfactory receptor neutrons, but this has yet to be proven. Further research needs to be done in this area but these studies do help demonstrate that the sense of smell in animals and humans has the ability to change and recover.
The chance of any recovery is likely to depend on the degree of damage caused, whether by a virus, head injury, or other factor.
We would recommend that smell training should not be viewed as a substitute for medical examination and treatment, where such is available but rather as an accompaniment to any prescribed treatment. Click here for details of clinics we have links with.
Smell Training Q&A
Many of the smell training research studies have used the same four smells – lemon, rose, clove and eucalyptus. However there’s no evidence to say these are the ‘right’ smells to use. You could certainly start with these, and change them regularly – see the next question. Choosing smells that you are familiar with and have memories of is a good idea. You can also use your other senses to help and use every opportunity to smell train whenever you can – when you eat an orange, use your senses of touch and sight to help you to recall memories, when you go for a walk, enjoy the breeze and look at the detail of the flowers whilst you take a sniff. All of this will help your regular, more formal smell training.
One group of participants in the 2015 ‘Modified Olfactory Training’ study (see main page text) changed to a different set of four smells every twelve weeks. The study suggests that this can potentially enhance success rates (note that the study was focused on people with post-viral olfactory loss).