Our sense of smell is really important to us. It warns us about dangers such as smoke or harmful chemicals. It gives us pleasure – a rose would not be as beautiful without its smell. It helps us to appreciate the flavours of food and drink (80% of the flavour of food comes from the smell).
Also, many smells are linked to important memories and those memories get recalled, often very strongly, when we smell a particular scent. This is a reminder that the sense of smell is not just about what happens in the nose. There are important nerve pathways in the brain which are involved in interpreting what the smell is and what it means (for example, danger or dinner?).
Previous studies have reported that the sense of smell can be affected in MS. This study looked at what aspects were affected.
50 people with either relapsing remitting MS or secondary progressive MS took part. Information was collected on their medical history, the characteristics of their MS, any depression, level of disability and the number of lesions seen on an MRI scan.
Well known tests for the sense of smell, which use Sniffin Sticks®, were carried out. Each Sniffin Stick is a bit like a pen and contains a different concentration of the smell being tested.
In a typical test, someone is blindfolded and given three pens, only one of which has an odor. The person has to say which pen they can smell or if none of them have a smell. If they can't correctly identify which one has the smell, they are given a new set but containing a pen with a higher concentration of the odorant. This is repeated until the researcher is sure at what concentration the person can detect that particular smell.
The sticks can also be used to work out how well someone can tell the difference between smells. In this test, they are given three pens and asked to identify which one has a different smell from the other two. This is repeated another five times with pens carrying different smells.
The researchers found that the aspect of smelling that was most affected by MS was the threshold concentration, when someone could first detect the smell. 40% of people in the study had anosmia which is the medical term for loss of the sense of smell. Those with a greater disability also had difficulty identifying what a particular smell was.
The researchers concluded that several aspects of the sense of smell were affected. In particular, those which required more thought, such as identifying a smell and telling the difference between several smells.
Rolet A, Magnin E, Millot JL, et al.
Olfactory dysfunction in multiple sclerosis: evidence of a decrease in different aspects of olfactory function.
Eur Neurol. 2012 Dec 19;69(3):166-170. [Epub ahead of print]
If you think that your sense of smell may be affected, the NHS has some suggestions on safety measures you might like to take. They are reproduced below.
It's recommended that you:
- install smoke alarms in all areas of the home, especially in the kitchen and near the fireplace
- change from natural gas appliances to electric
- clearly mark expiry dates on food and mark leftovers with dates so that you know when to throw them away
- carefully read warning labels on products such as bathroom and kitchen cleaners and insecticides, to be aware of potent chemicals
Cognitive difficulties are problems with thinking such as with memory, attention span or concentration. About half of all people with multiple sclerosis have some cognitive problems at some time. You can read more in the A to Z of MS.
Staying Smart is a website for people who would like to know more about managing cognitive problems. It contains examples of common problems such as:
- I forget where I have put things
- I can't say what's on the tip of my tongue
- At the end of the day I haven't got the important stuff done
- I forget to take my tablets
There are tips and tricks, gadgets and gizmos to help get around cognitive difficulties. You will also find suggestions on how friends and family, as well as health professionals, may be able to help. Publications and videos are available through the Staying Smart web site.
