Ask the Pharmacist

Q) Sometimes I get really strong smells, like rotting garbage, but no one else can smell them and there doesn’t appear to be a source. Am I going crazy?

A) No, you’re not crazy, or at least this isn’t enough to make that diagnosis stick. In fact, altered senses of smell are really quite common.

Nearly one in four Americans over the age of 40 report some distortion in their sense of smell and these numbers rise in older populations with 32% over the age of 80 complaining about this issue. In fact, 2/3’s of adults in a survey reported experiencing a problem with smell at some point during their lives.

There are a number of subcategories when it comes to smell disorders that are classified according to the nature of the disorder.

Anosmia is diagnosed when one loses the ability to detect any odours at all.

Hyposmia is described as a decreased sense of smell but those with this disorder still have some ability to detect odours. With this particular example, the name most likely used to describe it would be dysosmia which is defined as a distorted sense of smell. Of these three disorders, dysosmia seems to have the greatest negative impact on people’s ability to enjoy their lives so we will focus on this disorder.

Dysosmia itself can be broken down into two separate types. The first is parosmia (also called troposmia) which is a distortion in the perception of an odour. In other words, odours smell different from what one would expect. Parosmia may manifest itself in a number of different ways.

For some people, there is a loss of scent intensity meaning they cannot detect the full range of scents around them. Others may experience almost the opposite where everyday generally benign smells come across to these people as having an incredibly strong and disagreeable odour. In other words, the scent smells “wrong ” to them. For example, something as pleasant as the aroma of a fresh brewed pot of coffee may well smell like untreated sewage to them. In severe cases, the smell can be so overpowering as to cause the individual to become physically ill. It is estimated that about 6.5% of the population over the age of 40 have had to deal with parosmia with a preponderance of these being females. Other demographic groups which seem to have a higher incidence include Hispanics and Blacks as well those with lower amounts of education and/ or income.

Parosmia seems to be caused by damage to the olfactory neurons (these are the nerve cells responsible for detecting scents). These neurons line our nose, break down the smells and send the appropriate signals to our brains. The olfactory bulbs, which are located underneath the front of your brain, receive the information from these neurons and then tell the brain how to interpret all of the complex information that makes up a smell (i.e. does it smell foul, delicious or somewhere in between). Damage to either this bulb or the olfactory neurons fundamentally changes the way we experience assorted smells.

How does this damage happen? Well, probably the most common cause is from a cold or virus. In fact, parosmia has been linked to COVID-19 as well as better known afflictions such as the common cold or sinusitis. In a 2005 study of people with parosmia, just over 40% thought they believed their condition was related to an upper respiratory tract infection (this is the general term we use for the multitude of infections that can infect the nose, throat or bronchi of the lungs). Allergies are also a possible culprit. Not surprisingly, a brain injury from head trauma (or even a seizure) can fairly commonly lead to this disorder as well.

Just like everywhere else in the body, chronic exposure to the many toxins in cigarettes or other forms of air pollution can also sufficiently damage these neurons and predispose one to parosmia. Other possible causes include a number of nasty neurological conditions (such as Alzheimer’s, Lewy body dementia, Parkinson’s…), nasal polyps, a side effect of general anaesthesia, tumors located on the sinus bulbs or cavities (although this is rare) as well as radiation and chemotherapy that might be used to treat these and other types of cancer.

Deficits in certain vitamins and minerals are usually not the source of the problem but in rare cases may be (think zinc and the B vitamins) as could be medications you are taking for other health conditions (such as zinc nasal sprays, a bunch of cholesterol lowering drugs, a few blood pressure agents, a couple of common antibiotics and the thyroid replacement drug levothyroxine) although it is considered to be a relatively rare side effect.

Unfortunately for many, there is no known reason why their sense of smell suddenly goes haywire and we call these cases idiopathic. Parosmia isn’t typically a permanent condition and often does not require treatment. Neurons, like other cells, can repair themselves over time. The amount of time can vary widely but on average in long term cases it can take between two and three years to resolve. Short term cases last only a few days to weeks. Treatments can be both medical and lifestyle.

Some people engage in an activity called smell gymnastics. Here, they expose their nostrils to four different kinds of scents each day and try to retrain their brain to interpret them correctly. 25% of people who tried this over a 12 week period reported some improvement in their symptoms. As well, if the cause is smoking or other environmental pollutants, job number one is to limit exposure to these toxic chemicals.

Other treatments for parosmia include antibiotics, anticonvulsants, vitamin A, over the counter decongestant nasal sprays, zinc or the use of a nose clip to prevent smells from entering the nostrils (one would hope that most do not need to resort to this). For severe cases, surgery has been used and usually involves the removal of the olfactory epithelium but there are other procedures which may be tried as well.

The other type of dysosmia is called phantosmia. This condition is characterized by smelling odours that aren’t actually present. Its presentation can vary from one individual to the next in that it may be constant, or come and go or may be experienced in just one or both nostrils. Interestingly, (well, at least to me) the most common smells noted are that of burning rubber, cigarette smoke, chemicals such as ammonia and food that has spoiled. Possible causes are very similar to parosmia but also include migraines and dental problems. Phantosmia often goes away on its own as well but can be eased or eliminated via the use of nasal irrigation with saline, the use of over the counter decongestant sprays or the use of a anaesthetic nasal spray which can numb your olfactory nerve cells. For more information on these or any other health related questions, contact your pharmacist.