Loss of Smell (Anosmia)

What is Loss of Smell?

Loss of smell is a reduced or absent ability to detect odors. About 20% of people in the general population have some impairment of smell.^[1] Complete loss is called anosmia and partial loss is called hyposmia.^[2] It can lower quality of life, nutrition, social relationships and mental health.^[2]

Common symptoms

The main symptom is not smelling things as you used to, and because taste depends on smell, food can seem flat.^[1] Some people do not notice the loss at all until they miss a hazard, because smell loss often goes unnoticed and is diagnosed late.^[3]

• Not noticing smoke, natural gas or spoiled food, which can be dangerous^[1]
• Reduced enjoyment of eating and a change in appetite
• Smells that seem distorted, or odors perceived when nothing is there (phantosmia)^[4]

Causes and risk factors

The most common causes are sinus and nasal disease, viral infection and head or facial injury.^[1] Smell can be lost when something blocks odors from reaching the nasal lining (a conductive problem), or when the nerve cells or their pathways are damaged (a sensorineural problem).^[4]

Smell loss can also be an early sign of neurodegenerative disorders such as Alzheimer disease and Parkinson disease.^[1] Tobacco use is linked with poorer smell.^[1]

How it is diagnosed and treated conventionally

A physician, often an ear, nose and throat specialist, looks for the cause, and smell is measured with standardized tests such as the Sniffin' Sticks.^{[2, 5]} Treatment depends on the cause. Sinus surgery may be used for polyps, and corticosteroids may help when inflammation is the cause.^[1]

Smell training is the best-supported option for smell loss after a viral infection. It involves sniffing a set of odors twice a day over several months, and a meta-analysis of 13 studies found improvement in smell.^{[1, 5, 6]} Short courses of steroids are an option in selected patients, and trials do not clearly show added benefit when steroids are combined with training.^{[5, 7]}

Many people recover on their own. Up to 60% of those with smell loss after infection and up to 20% of those after head injury improve without treatment, which makes it hard to judge any therapy without a control group.^[1]

Why Loss of Smell calls for a whole-person approach

Smell loss has several possible causes, and it affects eating, safety and mood. The factors below are why it is worth looking beyond the nose alone.

Care that pays attention to these linked factors is a reasonable addition to medical evaluation. It does not replace finding the cause.

Sinus and nasal inflammation

Inflammation of the nose and sinuses is among the most common causes of smell loss.^[1] In a review of 28 trials in chronic sinusitis with nasal polyps, oral and topical steroids improved smell, while herbal products, antibiotics and antifungals showed no overall effect on smell scores.^[8]

Viral infection and nerve recovery

After a viral infection, the smell-sensing nerve lining may be damaged, and recovery can take months.^{[1, 5]} Smell training is thought to work through the plasticity of the olfactory system, although the exact mechanism is still being studied.^[6]

Mood and wellbeing

Smell loss can erode quality of life and mental health.^{[2, 3]} A meta-analysis found that people with depression scored lower on smell tests than people without it, which shows an association rather than a cause.^[9]

Safety and nutrition

Because food loses its flavor and warning smells go unnoticed, people with smell loss need practical safeguards such as working smoke and gas detectors.^{[1, 3]}

Acupuncture for Loss of Smell

What the research shows

Acupuncture has been tested for smell loss in small trials, and the evidence is limited. In a sham-controlled trial of 60 people with smell loss after an upper respiratory infection, real acupuncture improved the overall smell score more than sham acupuncture. The gain came mostly from odor discrimination and was larger in people with a shorter duration of loss.^[10]

A trial of 40 people with smell loss after COVID-19 compared two sessions of ear acupuncture with a switched-off laser. Both groups used steroid nose drops, and self-rated smell improved more with real treatment. Three people had brief nausea, headache or dizziness.^[11]

A systematic review of traditional Chinese medicine for post-viral smell loss found 6 randomized trials with 545 participants plus smaller non-randomized studies. Most used acupuncture or acupoint injection, and five trials favored treatment, but the overall quality was low.^[12] A broader review of acupuncture in ear, nose and throat conditions found that conclusions were limited by differing methods and that higher-quality trials are needed.^[13] The evidence for smell loss from causes other than viral infection is thinner still.

How acupuncture may work

How acupuncture might affect the sense of smell is not established. The trials above measured smell, not mechanisms, so any explanation remains a hypothesis.^{[10, 12]} Smell training, which has stronger support, remains the standard non-drug approach.^[5]

What treatment involves

Treatment uses fine, sterile, single-use needles placed at points on the face, head, hands and legs, usually left in place for about 20 to 40 minutes. The ear acupuncture trial above used two sessions one week apart, and we reassess after a short course of visits.^[11]

Serious problems from acupuncture are rare. In prospective studies, about 9 in 100 patients had a minor reaction such as brief bleeding, soreness or redness at a needle site, and serious events occurred in about 1 in 10,000 patients.^[14] Tell the practitioner first if you have a bleeding disorder, take blood thinners, are pregnant, or have a pacemaker (relevant to electroacupuncture).

Ayurvedic medicine for Loss of Smell

The Ayurvedic view

Ayurveda traditionally treats the nose as the gateway to the head, and loss of smell is understood as a disturbance in the nose and head region. In this framework, a Kapha imbalance causing congestion, or a Vata imbalance affecting sensation, may be considered. These are traditional categories for choosing treatment, not biomedical diagnoses.

Therapies that may be used

Care is chosen for the individual and traditionally combines:

• Diet and daily routine intended to calm Kapha or Vata, such as warm foods and regular sleep
• Steam inhalation and gentle warm-oil practices for the head and neck
• Nasya, the placing of herbal oils or powders in the nose, which is the Panchakarma therapy traditionally used for the nose and head

Panchakarma procedures are not appropriate during pregnancy, acute illness or frailty. Nasal therapies should wait until a physician has found the cause of smell loss and ruled out an infection or a structural problem.

What the research shows

There is no clinical research on Ayurvedic treatment for loss of smell. We found no trials or systematic reviews, so any benefit is unknown. The nearest research is on chronic sinusitis, a common cause of smell loss, where a systematic review of 13 Ayurvedic studies found reported improvement but a significant risk of bias in every study.^[15] Because many people with post-viral smell loss improve on their own, an apparent improvement after any treatment cannot be taken as proof that the treatment worked.^[1]

Herbal medicine for Loss of Smell

Herbs and formulas that have been studied

Research on herbs for smell loss is sparse. A lavender syrup has been tested in COVID-19-related smell loss, and ginkgo has been evaluated for smell loss after a viral cold.^{[16, 17]} Chinese herbal medicine has been grouped with acupuncture in reviews of post-viral smell loss, but the controlled studies mainly tested acupuncture and acupoint injection.^[12]

What the research shows

The evidence is very limited. In a pilot trial of 43 outpatients with COVID-19, those who took lavender syrup had a larger drop in self-rated smell loss than those who did not. The study was small, its control group received no placebo, and symptoms had lasted only about a week, so natural recovery may explain much of the change.^{[1, 16]}

A review of herbal medicine in ear, nose and throat practice concluded that ginkgo taken by mouth has no indication in smell loss after viral rhinitis.^[17] In the sinus polyp trials above, herbal products did not change overall smell scores.^[8]

Safety and herb-drug interactions

Herbs are active substances and can interact with medicines. Ginkgo has been linked to bleeding when combined with warfarin or aspirin, and case reports describe bleeding when warfarin was combined with herbs including dan shen, dang gui, ginger and Boswellia.^{[18, 19]} People taking blood thinners need a practitioner's review before using herbs.

In one study, about one fifth of Ayurvedic products bought online contained detectable lead, mercury or arsenic.^[20] Herbs should come from tested sources and be prescribed individually. Tell us if you are pregnant or breastfeeding, have liver or kidney disease, take blood thinners, or have surgery planned.

Translating traditional medicine into modern biological language

The links drawn here are interpretation, not equivalence. Chinese medicine would describe smell loss as a nose orifice that is not open, with patterns such as lung qi weakness or dampness blocking the nose. Researchers might loosely compare this with nasal inflammation and swelling, or with injury to the olfactory nerve cells.^[1]

Ayurveda's Kapha-type congestion likewise parallels blocked airflow to the smell lining. No study has shown that a dosha or a qi pattern corresponds to a specific biological process in smell loss.

How this care fits with your medical care

Integrative care for smell loss is complementary. Keep your physician or ENT specialist, and do not stop or change prescribed steroids or other medicines without your prescriber. We do not diagnose the cause of smell loss, and any new or unexplained loss should be medically evaluated.

Please bring your diagnosis, any imaging or smell-test reports, a full list of medicines and supplements, and details of any sinus surgery or head injury. Smell training is a medically supported step that can be done alongside our care.^[5]

When to seek urgent medical care

Most smell loss is not an emergency, but some features need prompt medical assessment, because smell loss can be a sign of serious nose, sinus or brain conditions.^[1]

• Sudden smell loss after a head injury
• Smell loss with a severe headache, confusion, weakness or vision changes
• Smell loss with a nosebleed, a one-sided blocked nose or a growth in the nose
• Swelling, redness or pain around an eye
• Inability to detect smoke or gas leaks when you live alone

If any of these occur, call 911 or go to the nearest emergency department.