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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?

In recent years there have been a number of studies that have shown this to be the case.  For example, 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.  Plailly and Royet 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.

This developed ability to imagine scents is borne out by perfumers themselves, who spend years smelling and learning the scents of a huge variety of fragrance ingredients.

Can smell training benefit people who have suffered olfactory loss?

So if training the sense of smell works for people with full olfactory ability, can it also help those affected by anosmia or hyposmia?  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 anosmics, 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 synthetic oils – rose, eucalyptus, clove and 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.

 What does this mean for someone affected by anosmia or hyposmia?

Successful treatment for smell loss is still in its infancy, but Prof. Hummel’s study does give some hope for people who have suffered 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 led to people becoming able to detect other scents in their environment, rather than just the scented oils applied to cotton pads and held under the nose.

That said, the other 70% of patients in Prof. Hummel’s test group did not experience any improvement in their ability to detect odours, and there is very little information as to why the smell training worked for certain people and not for others but may represent the amount of nerve/receptor damage caused by the original insult.  Further research needs to be done in this area, but this study is one of several that shows that the sense of smell in animals and humans has the ability to change and recover. Ironically the precursor cells that the lining of the nose that detects smell arise from have the best ability to regenerate and are often used for research in repairing damage to other nervous tissue in the body.

Naturally, we would recommend that smell training should not be viewed as a substitute for medical examination and treatment at a smell and taste clinic, but rather as an accompaniment to any prescribed treatment.

I suffer from anosmia or hyposmia – how do I try smell training?

Before we explain how to perform the smell training, it is worth looking briefly at why Prof. Hummel chose the four particular fragrances used in his study.

Attempts have been made to categorise smells, in the same way that tastes have been classified as being sweet, sour, salty and bitter.  In 1916 German psychologist Hans Henning developed a model for this which he called the ‘odour prism’, classifying smells as flowery, foul, fruity, spicy, burnt and resinous.  Prof. Hummel chose scents to represent four of these categories (or if you like the range of smell) for his study, as shown below.  In this way the olfactory system of the person undertaking the training is being stimulated by a range of different types of odours.

Flowery – Rose

Fruity – Lemon

Spicy – Cloves

Resinous – Eucalyptus

The next step is to source the scents themselves.  Given that it is not practical to buy a bunch of roses every few days over the duration of the training period (Prof. Hummel recommends that the training be done for six months rather than the twelve week period over which he ran the study), another source of the fragrances must be found.  We have found that essential oils (pictured above) are effective and are at least extracted from the natural substances themselves rather than being synthesised in a laboratory.  They are also readily available to buy online or in health/beauty shops.

Instructions for performing the training are below.  Please bear in mind what we have said above, that this may not work for you, and that the training is no substitute for a medical appointment with an expert in diagnosing smell and taste disorders.  Visit the Smell and Taste Clinics page of the website for details of such clinics around the world.

You will also need a good supply of perfume testing sticks, or cotton pads

1 – Pour a few droplets of one of the oils on to a testing stick or pad

2 – Do not try to sniff the stick/pad immediately; leave it for a few minutes for the fragrance to develop

3 – Hold the first stick/pad up to your nose, about an inch away.  The order in which you test the oils does not matter

4 – Relax and try to inhale naturally through the nose – sniffing too quickly and deeply is likely to result in you not being able to detect anything

5 – Try this a couple more times, then rest for five minutes

6 – Move on to the next oil and repeat as above.

If you cannot smell anything at first then do not be disheartened.  The anosmia sufferers we have spoken to who have tried this process themselves experienced varying degrees of success, and it took some of them over a week of trying before they started to detect any of the odours.  Just remember that the studies we have talked about here have shown that the sense of smell can change and recover, and that it can be trained and developed with exposure to odours, as expert perfumers will testify.  Good luck!

If you do decide to undertake this yourself then we would like to hear from you; please emailinfo@fifthsense.org.uk and tell us about your experience as it may be beneficial to others

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