Anosmia 

  • Overview

Introduction 

Congenital anosmia

It's very rare to have congenital anosmia, which is where you are born with no sense of smell because of a genetic condition or faulty gene. People with congenital anosmia have a lifelong inability to smell and have no concept of what a smell even is.

It can occur alone (isolated congenital anosmia) or it can be a symptom of another genetic condition, such as Kallmann syndrome or Klinefelter syndrome.

Currently, there is no known cure or treatment for congenital anosmia.

Safety measures

If you have anosmia, you'll need to take special precautions because you won't be able to smell fires, poisonous fumes, leaking gas or food that has gone off.

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

Anosmia is the medical term for loss of the sense of smell. It is usually caused by a nasal condition or brain injury.

However, an estimated 6,000 people in the UK are born without a sense of smell. This is known as congenital anosmia.

Losing your sense of smell can be very depressing and isolating. It means missing out on many experiences most of us take for granted, such as smelling fresh flowers, perfume or the scent of a loved one.

Smell also plays an important role in how you taste things. Many people with anosmia lose interest in food, because 80% of the flavour of food comes from smell.

If you have suddenly lost your sense of smell and don't know why, see your GP for a diagnosis of the underlying cause. They may be able to treat this and restore your sense of smell.

What are the causes?

There are several medical conditions and medications associated with a loss of smell. The possible causes include:

  • a viral infection affecting the upper respiratory tract, such as a cold 
  • persistent rhinitis and sinusitis, with or without nasal polyps 
  • a nose abnormality such as a crooked nose or a nasal septum (wall dividing the nostrils) that is not straight 
  • hay fever that causes severe inflammation of the nasal passages
  • certain medication, including antibiotics such as metronidazole
  • recreational drug use such as crack cocaine
  • diabetes
  • long-term alcoholism
  • an underactive thyroid
  • Cushing's syndrome (high levels of the hormone cortisol in the blood) 
  • exposure to a chemical that burns the inside of the nose   
  • head injury
  • brain tumour
  • Kallmann syndrome – a genetic condition present at birth, where the nerves from the nose to the brain fail to connect
  • radiation therapy to the head and neck
  • epilepsy
  • Parkinson's disease
  • Alzheimer's disease
  • stroke
  • liver or kidney disease
  • vitamin B12 deficiency
  • schizophrenia
  • granulomatosis with polyangiitis  an uncommon disorder of the blood vessels
  • sarcoidosis  a rare disease that causes body cells to form into clumps 

In general, anosmia is usually caused by either a problem with odours getting to the top of the nose (because of swelling or a blockage in the nose) or a problem with nerve signals from the nose to the brain.

However, in some cases the cause cannot be found  this is known as idiopathic anosmia.

Getting diagnosed

Your GP will want to take your full medical history, examine the inside of your nose and take a blood sample for testing in a laboratory.

You may need to be referred to hospital for further tests such as a CT scan or nasal endoscopy (where a thin tube is inserted up your nose to have a look deep inside). This is to rule out more serious possible causes.

Your GP may refer you to the UK's own NHS Smell and Taste Clinic, which is based at James Paget University Hospital in Gorleston, near Great Yarmouth.

Can anosmia be cured?

Whether or not anosmia can be cured depends on the underlying cause.

If anosmia is the result of a genetic condition that was present at birth, it will probably be something you have to live with for the rest of your life.

However, in 50% of cases anosmia is potentially reversible  it can be improved or cured when the underlying condition is treated. For example, if the cause is swelling in the nose or sinuses, steroids can usually clear this up and restore your sense of smell.

Treatments that may help, depending on your condition, are:

However, the above treatments may come with unpleasant side effects. Speak to your doctor about whether any of these treatments may be suitable for you and, if so, what side effects you may experience.

BiCASS

The NHS Smell and Taste Clinic offers a sophisticated procedure known as bilateral computer-aided endoscopic sinus surgery (BiCASS). In BiCASS the surgeon opens all your sinuses and clears them out to reduce inflammation and allow nasal rinses and sprays to reach them.

This treatment can bring back some sense of smell for many people with anosmia. However, if you don't keep taking your nasal medications afterwards, the anosmia is likely to return.

If you've had surgery to remove nasal polyps, it is quite common for these to grow back and many people find they need another operation. However, BiCASS may reduce the need for further surgery. 

recent review looked at how successful BiCASS was in treating patients with persistent sinusitis, some of whom also had nasal polyps. Data from 20052009 showed that only four patients out of 141 (3%) needed to have further surgery after having BiCASS as their first operation.

Page last reviewed: 29/11/2012

Next review due: 29/12/2014

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