Viral Anosmia:

Frequently Asked Questions With Answers From Mick O'Hare©

A Note From The Editor, Karl L. Wuensch

   I met Mick through the now defunct Anosmia Community at Yahoo. He was one of the most active members of that group. Mick developed viral anosmia in June of 1998. He has educated himself regarding the causes and treatment of this condition and has shared his knowledge, and personal details of his experience, with others.

   Below are a number of questions and answers relating to viral anosmia, how it affected me and my subsequent treatment and recovery from it. This is not meant to be a full treatise on the condition, but it answers a few of the common questions I am often asked, including whether the Covid-19 coronavirus can cause similar symptoms. Evidence suggests that it can. Readers should bear in mind that I have no medical training.

What is viral anosmia?

   Viral anosmia is a total lack of olfaction caused by an upper respiratory infection (URI) virus destroying the cells of the olfactory epithelium through a process known as necrosis. Covid-19 acts in the same way. The virus enters the cells and destroys them from within leading to a lack of smell. Usually only the olfactory receptor cells are destroyed but some doctors believe the olfactory nerve or the nasal serous glands can also be damaged.

How do I know if I have viral anosmia?

   You don't for sure because the diagnosis is one of absence. If no other cause can be found it is likely to be caused by a virus. In many cases the rapid, immediate onset of anosmia can be traced to an incidence of URI (a cold, influenza, coronavirus or sinus infection). This is usually enough to convince a physician that the URI was the cause, but by the time a patient visits a doctor, the virus itself has often gone. Concurrent URI and anosmia usually indicates viral-induced anosmia, but care must be taken to rule out other causes. 

What if I didn't have any symptoms of cold or 'flu?

   Remember that 25% of rhinoviruses (the viruses that cause colds) have no symptoms. Often Covid-19 is asymptomatic too. The virus may be present in your nose but that doesn't mean you'll have a sore throat and streaming nose. It is possible that the only symptom may be the anosmia itself. Your doctor may describe this condition as idiopathic anosmia (or anosmia with no known cause) - however, this may still be a case of viral anosmia.

Does a specific virus cause anosmia?

   Nobody is certain, although it seems unlikely. Any URI virus seems capable of causing anosmia if its protein coat matches a key on your olfactory cells. Covid-19 too seems to cause anosmia in some, but not all, cases. It appears that viral anosmia is a matter of bad luck: the virus cells match an individual's olfactory receptor cells in very few cases. But in those in which it does, viral anosmia occurs.

Can a virus also destroy my taste as well?

   Yes it can. In my case this happened. Remember that true taste from the tongue's tastebuds comprises only salt, sweet, bitter and sour - and possibly a fifth taste known as umami - see the document Anosmia and Taste. Most of what we perceive as taste is actually flavour, a process almost identical to smelling that is generated by the olfactory receptors as food is chewed and its odour rises through the back of the nose to be detected as flavour. In most cases of viral anosmia smell and flavour are lost when the olfactory epithelium is destroyed but taste remains intact. In my case all three were lost, but I must stress that this is a rare scenario.

Is the virus still present and causing my anosmia?

   No, the virus dies quickly when attacked by the body's immune system. Usually, by the time viral anosmia is apparent and diagnosed, the virus that caused it is long dead.

Do people recover from viral anosmia?

   Yes they do. Some recover spontaneously. The recovery rate is not known - figures are vague and badly researched, ranging from 18% of all cases in one study to 66% in another. Yet another study suggests that two thirds of all viral anosmia victims will have recovered at least some of their smell within four years. Bearing in mind that 'some of your smell' is arguably as little as 1% and that four years is a long time, this is not a good prognosis. However, many people who become viral anosmics and recover quickly will not report their situation to any medical practitioner so it can be assumed that more people recover than have been recorded in any study. The cells of the olfactory epithelium can regenerate, so spontaneous recovery is certainly possible.

So others do not recover?

   Some people do not recover at all and remain permanently anosmic. Others recover partially, others recover tastes and smells that are distorted.

What are distorted smells?

   Most - if not all - people, when recovering from viral anosmia, seem to go through a phase where their smell and flavour perception is distorted. This is known as parosmia. Smells are either inaccurate, dreadfully unpleasant or both. Many people pass through this phase to normal, or near normal perception, although it is often still reduced in acuity. Others remain stuck in the distorted phase, which can be terribly depressing.

Is there any treatment for the symptoms of viral anosmia?

   The standard medical line is that viral anosmia is not treatable and nearly all physicians will say that this is the case. At present, as far as I am aware, only Dr Robert I Henkin of the Taste and Smell Clinic in Washington DC, USA offers treatment for the condition with varying reports of success. After contracting viral anosmia in June 1998 I was first treated by Dr Henkin in May 1999. No 'alternative' therapies have proved to be successful. You can read the story of my illness, treatment and the medical science behind in a feature I wrote in 2005 for the British weekly science magazine New Scientist, for which I work:  The Unbearable Absence of Smelling. If you would prefer to finish the FAQ before reading the feature, the link is repeated at the foot of the page

What form did the treatment take?

   After numerous physical and chemical (blood, urine, saliva, nasal mucus, etc) tests I was diagnosed as a viral anosmic with parosmia. I was treated immediately with haloperidol, an antipsychotic drug. Dr Henkin told me I was suffering from parosmia because my brain was failing to interpret correctly the signals from my damaged olfactory receptors. Later, in November 1999, when the distortions had diminished but actual smell/flavour acuity failed to improve he suggested I take another drug called theophylline (a well-known drug more widely used for treating asthma). This drug increased the presence in my olfactory cells of a growth factor known as cyclic AMP and found in nasal mucus. Cyclic AMP acts on olfactory stem cells allowing them to create new cells which carry odour to the olfactory nerve and are necessary for humans to be able to smell things. At first the theophylline seemed to have little effect, so, in February 2000 and again in October 2000, I took a very short course of oral steroid - dexamethasone - to kickstart the olfactory process. This was successful and was measured both objectively in the clinic and subjectively, by myself. All the drugs were taken in pill form.

Was the treatment successful?

   Apparently yes. The haloperidol quickly reduced the level of distortions and theophylline (especially after the two bursts of dexamethasone) has gradually improved my acuity to the point where it is now fully restored. Of course, one person's success is not cast-iron proof that the treatment works.

How did my viral anosmia start?

   It began with a sore throat that became progressively more painful for a week following which a very stuffy head cold began, with a cough, fatigue and painful limbs. After congestion began, anosmia set in. However, the viral symptoms can vary widely.

How long did recovery take?

   I suffered with parosmia from around August 1998 to May 1999 when I began treatment with haloperidol. The distortions were gone within three weeks. Acuity recovered more slowly. Treatment for this using theophylline began in November 1999 and, to date, progress has been slow and gradual. My acuity is now around 100%. However, progress was not linear, there were many ups and downs - one day I'd taste something, a week later it would be gone again, only after time did flavours/smells return and persist. I also suffered for a long time from taste extinction - I'd taste the first mouthful of a food or drink, and subsequent bites would have no flavour. I still experience this on occasion.

Do the drugs have any side-effects?

   They can do. Haloperidol is a strong antipsychotic and can cause drowsiness, insomnia, depression and some central nervous system effects such as a marked twitching of the hands. However, the doses used in treatment for parosmia are tiny - I took only 0.5mg per day which my own GP described as minuscule. I had no side-effects at all. Theophylline is a xanthine , a group of drugs which includes caffeine and its side-effects are almost identical, including nausea, headache, gastrointestinal disturbances, palpitations and insomnia. I started on a dose of 400mg per day in November 1999 and moved up to 600mg in February 2000. Side-effects usually present themselves immediately with theophylline and rarely appear with prolonged dosage, in fact there are no known long-term dangers in taking this drug. I have probably had more headaches and neck ache since taking the drug but no really bad effects at all. In any case, the benefit outweighs the disadvantages. I have now moved back to 150 mg every other day. The dexamethasone is a corticosteroid and there are many unpleasant effects associated with such drugs taken long-term. However, my course was 24mg taken over the course of two days on two separate occasions. I was sleepless on both occasions but this may have been due to the jetlag experienced from my flight from London to the clinic in Washington DC. I noticed no other side-effects. Do not self prescribe any drug - make sure you have a full diagnosis from a physician before any treatment.

Could the recovery have been spontaneous?

   It could have, although the coincidences were remarkable. Within three weeks of starting haloperidol, the distortions were gone, as predicted by Dr Henkin. Treatment with theophylline was also successful, although much slower than Dr Henkin suggested. However, the two treatments with dexamethasone , both boosted olfaction - objectively and subjectively. What convinced me of the efficacy of theophylline was that when, unilaterally and much, I suspect, to Dr Henkin's irritation, I tried to wean myself off theophylline, I began to suffer olfactory loss again. This was after three years of apparently successful theophylline treatment. Restarting theophylline restored olfaction. Bear in mind, however, that many physicians and ENTs eschew Dr Henkin's theories. The bottom line is I have no proof that his treatment worked because I am a single case that could just amount to a series of coincidences. Other people have had different experiences and outcomes with the treatment. However, I personally am reasonably satisfied that the treatment was successful in my case.  Dr. Henkin’s paper from the American Journal of Medical Science discussing the efficacy of theophylline was published in June 2009.  If you find the abstract interesting, head on down to your local university library to retrieve the full article.

What else might I expect?

   Very often, late-onset (ie non-congenital) anosmics suffer from depression and viral anosmics are no different. I found the depression very intense, others find it easier to cope. But in the first few months the feelings can be very powerful and people, on very rare occasions, have been known to contemplate suicide. If the depression is particularly bad you should see a healthcare professional without delay. The situation is often exacerbated by the fact that unless they have experienced anosmia, your friends and family may consider that your complaint sounds trivial and you will encounter statements such as 'It could be worse' or 'at least you don't have to smell the cat litter'. You may need to explain that such comments are not helpful.

If I think I'm a viral anosmic, what should I do?

   First you should rule out any other cause for anosmia (the second most common cause is a blow to the head), some of which, in rare cases, can be life-threatening. Insist on an MRI, CAT scan and a sinus X-ray and also a visit to an ENT doctor. However, if you can match your anosmia to a single instance of URI with no previous history of allergic or sinus infection then it is highly likely that your anosmia is of viral origin.

What other conditions might I have?

   The differential diagnoses of viral anosmia are many. They range from inflammation caused by allergies or sinus infection, through head injury, to tumours of the olfactory groove and frontal lobe of the brain. Be reassured though, that such tumours generally cause anosmia with a gradual onset. Viral anosmia is almost instantaneous.

Are there any reliable sources of information regarding viral anosmia on the internet?

   Tangible, reliable info is few and far between and all the major anosmia sites and discussion forums are already detailed on the home page of this website.

Taste extinction

    In response to queries about "taste extinction," Mick noted that this term is used by Dr. Henkin, and he explained it, in layman's terms, in this way:  "This occurs because olfactory cells can only fire once every so often. If you have fewer than the normal quotient they all fire upon the first contact with an odour (or flavour) and are used up in that first instance.  In people with a normal olfactory system the cells share the workload, and taste/smell can be maintained for much longer. however, even in those with normal systems, tastes/smells diminish after the first bite, just not by as much.


Last updated 14-April-2020.

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