Causes of Loss of Sense of Smell and Taste

Inability to Detect Odours and Flavours is Common and Often Benign

Jan 26, 2009 John Richard Roberts

Problems with smell and taste are common and unpleasant but usually not serious. Because the brain processes these two senses together taste is dependent on a good nose.

Most people have experienced a temporary reduction in their sense of smell and the loss of taste that goes with it. It only takes a bout of the common cold to block the nasal passages and make food tasteless.

Problems with smell and taste are not normally life threatening but clearly can affect the quality of life making eating a chore rather than a pleasure. However the consequences of loss of smell and taste can be serious if toxic substances can't be smelt or infected food can't be tasted.

Disorders of Smell

• Blocked nose: from colds or polyps etc.
• Infections: Many types of infection can damage the nasal nerves and nasal epithelium.
• Abscesses.
• Damage to the nerves: that from the head injury is one of the commonest causes.
• Allergies – hay fever for example.
• Tumours – rare but benign and malignant tumours can occur in the nose and sinuses.
• Brain disorders: people with temporal lobe epilepsy can experience strange smells (olfactory hallucinations) and degenerative disorders may affect the olfactory nerves.
• Brain infections.
• Aging: as with the other senses it's common for the sense of smell to deteriorate with age.

Disorders of Taste

• Dry mouth: this is the most common reason. Saliva is needed to appreciate taste properly. Some drugs cause dry mouth and it's part and parcel of some diseases such as Sjogren's syndrome – a type of arthritis.
• Nerve damage: Bell's palsy is a disorder of the facial nerve which supplies part of the tongue.
• Heavy smoking: affects taste and also sense of smell.
• Damage to tongue: burns or chemical irritation.
• Nutritional deficiencies: particularly lack of copper, zinc and nickel.

Anatomy of Smell and Taste

Small hairs (cilia) project from the membrane lining the nose. These hairs are receptors for odours in the air that is breathed in, they can detect minute quantities of chemicals that make up these odours. When a receptor is stimulated by an odorous chemical a nerve impulse is sent along the olfactory nerve to the smell and taste centre in the brain.

The tongue has thousands of taste receptors situated in taste buds on its surface. These detect five main flavours in food: salt, bitter, sweet, sour and savoury (monosodium glutamate). Impulses from the receptors pass through several nerves to the smell and taste centre.

It is in this centre that impulses from the nose and taste from the tongue are integrated and appreciated as flavours. This why smell is so important for the proper functioning of taste.

Information from this centre is sent to the temporal area of the brain where memories of taste and smell are stored.

This article is for information only. If you have any health concerns you should consult your doctor.

Resource

Neurophysiology by RHS Carpenter. 2002

The copyright of the article Causes of Loss of Sense of Smell and Taste in General Medicine is owned by John Richard Roberts. Permission to republish Causes of Loss of Sense of Smell and Taste in print or online must be granted by the author in writing.

Odour Receptor

Taste Bud