Loss of Smell
A reduced or absent sense of smell, known medically as anosmia
Quick Facts
- What it is: Reduced or absent sense of smell
- Common causes: Colds, sinus disease, viral infection
- Often linked to: Reduced sense of taste
- Seek care if: Sudden loss, head injury, or it persists
Overview
Loss of smell, called anosmia when complete and hyposmia when partial, means that the nose and brain are no longer detecting odors normally. Because much of what we experience as flavor actually comes from smell, people with reduced smell often say food tastes bland or that they have lost their sense of taste as well.
Smell works when odor molecules reach a small patch of nerve tissue high in the nose and send signals along the olfactory nerve to the brain. Anything that blocks air from reaching this area, damages the nerve, or affects the brain regions that interpret smell can reduce or remove the sense of smell. Many cases are temporary and improve once the underlying cause clears, but some can be long-lasting.
Common Causes
Loss of smell usually falls into two groups: blockage that stops odors reaching the smell nerves, or damage to the nerves or brain themselves.
- Nasal and sinus conditions: The common cold, sinusitis, allergic rhinitis, and nasal polyps cause swelling and mucus that block airflow.
- Viral infections: Some viruses, including those causing colds and COVID-19, can directly affect the smell nerves.
- Head injury: A blow to the head can tear or bruise the delicate olfactory nerve fibers.
- Aging: The sense of smell naturally fades with age.
- Neurological conditions: Parkinson disease and Alzheimer disease can reduce smell, sometimes years before other symptoms.
- Medications and irritants: Certain drugs, smoking, and chemical exposures can dull smell.
Associated Symptoms
The symptoms that accompany loss of smell often point to the cause. A blocked nose with smell loss usually suggests a cold, allergy, or sinus problem, while smell loss without congestion may suggest a nerve cause.
- Nasal congestion, runny nose, or postnasal drip
- Reduced or altered sense of taste
- Facial pain or pressure with sinus disease
- Sneezing and itchy eyes with allergies
- A distorted sense of smell, where normal odors smell unpleasant (parosmia)
- Memory changes or tremor when a neurological condition is involved
Diagnosis & Evaluation
A clinician will ask how the smell loss began, whether it was sudden or gradual, and what other symptoms are present. The history alone often points to the cause.
- Nasal examination: Looking inside the nose for swelling, polyps, or signs of infection, sometimes with a thin lighted scope (endoscopy).
- Smell testing: Scratch-and-sniff or other standardized tests measure how well odors are detected.
- Imaging: A CT scan of the sinuses or an MRI of the brain may be used when a structural or neurological cause is suspected.
- Allergy testing: Considered when allergic rhinitis is likely.
Treatment & Management
Treatment depends entirely on the cause, and many cases improve on their own once an infection or inflammation settles.
- Treating nasal and sinus disease: Saline rinses, steroid nasal sprays, allergy medicines, or treatment of infection can reopen blocked passages.
- Removing polyps: Medication or, in some cases, surgery can clear nasal polyps that block airflow.
- Smell training: Repeatedly sniffing a set of familiar scents over weeks to months may help recovery after a viral infection.
- Stopping irritants: Quitting smoking and avoiding chemical fumes can help smell return.
- Time: Smell loss after a viral illness often improves gradually, though it can take months.
Self-Care & Prevention
While not every cause can be prevented, some steps protect your sense of smell and keep you safe when it is reduced.
- Treat allergies and sinus problems promptly
- Avoid smoking and secondhand smoke
- Wear protection when working with strong chemicals
- Install smoke and gas detectors, since you may not smell smoke or a gas leak
- Check food expiration dates carefully, as you may not detect spoilage by smell
When to See a Doctor
See a doctor if your sense of smell does not return after a cold clears, if it is lost suddenly without an obvious cause, or if it follows a head injury. Seek prompt medical care if loss of smell comes with:
- A recent significant head injury
- Severe headache, neck stiffness, or confusion
- Weakness, numbness, or trouble speaking
- Memory problems or tremor
These features can signal a neurological problem that needs urgent evaluation.
Frequently Asked Questions
Why have I lost my sense of smell after a cold?
Colds and other viral infections cause swelling and mucus that block odors from reaching the smell nerves, and some viruses affect the nerves directly. Smell usually returns as the infection clears, though recovery can sometimes take weeks to months.
Is loss of smell ever permanent?
It can be. Smell loss from head injury or long-standing nerve damage may not fully recover, while loss from colds, allergies, and sinus disease usually improves once the cause is treated. Smell training may help some people regain it.
Why does food taste bland when I cannot smell?
Much of what we call taste is actually smell. When the sense of smell is reduced, the tongue still detects basic tastes like sweet and salty, but the rich flavors that come from aroma are lost, so food seems bland.
Can loss of smell be a sign of a serious condition?
Most cases are due to colds, allergies, or sinus problems and are not serious. However, sudden unexplained smell loss, loss after a head injury, or smell loss with memory changes or tremor should be evaluated, as it can sometimes signal a neurological condition.
What is smell training?
Smell training involves sniffing a small set of strong, familiar scents, such as lemon, rose, clove, and eucalyptus, twice a day for several weeks or months. It is a simple, low-risk way to encourage recovery, especially after a viral infection.
References
- National Institute on Deafness and Other Communication Disorders (NIDCD). Smell Disorders.
- Mayo Clinic. Loss of smell (anosmia).
- MedlinePlus, U.S. National Library of Medicine. Smell - impaired.
- American Academy of Otolaryngology-Head and Neck Surgery. Smell and Taste.