What Parosmia and Anosmia Are
Anosmia is the complete loss of olfactory capacity, while hyposmia represents partial reduction. Parosmia is a qualitative distortion of smell — odors that should be neutral or pleasant (coffee, garlic, meat) are perceived as foul, burnt, or nauseating, causing significant impact on eating and quality of life.
The most common cause today is post-viral, especially after COVID-19 (where anosmia affected up to 80% of those infected in early phases) and influenza. In COVID-19, the mechanism is unique: SARS-CoV-2 infects the sustentacular (supporting) cells of the olfactory epithelium — which express ACE2 — without directly infecting the olfactory neurons. The death of sustentacular cells deprives the neurons of trophic support, leading to anosmia. Parosmia emerges during regeneration, when olfactory axons reconnect erratically to the olfactory bulb — aberrant connections generate distorted perceptions.
Impact on Eating and Quality of Life
Conventional Treatments
Therapeutic options for post-viral anosmia/parosmia are limited, with most studies presenting low to moderate quality of evidence. Olfactory training is the intervention with the best scientific support.
TREATMENTS FOR POST-VIRAL ANOSMIA/PAROSMIA
| INTERVENTION | MECHANISM | EVIDENCE |
|---|---|---|
| Olfactory training (1st line) | Stimulates olfactory neuroplasticity; 4 aromas 2x/day | B — only one with multiple positive RCTs |
| Intranasal corticosteroid | Reduces inflammation of the olfactory epithelium | C — adjunct in associated mucosal edema |
| Intranasal vitamin A (retinol) | Neurotrophic; stimulates olfactory neuronal regeneration | C — preliminary positive results |
| Alpha-lipoic acid (600 mg/day) | Antioxidant; reduces oxidative neuronal damage | C — weak evidence; low cost |
| Intranasal PRP | Intra-olfactory platelet growth factors | C — preliminary; under study |
| Carbamazepine | Intense parosmia / refractory phantosmia | C — off-label use; monitor side effects |
How Acupuncture Works in Anosmia and Parosmia
Acupuncture stimulates the regeneration of the olfactory epithelium through neurotrophic and neurovascular mechanisms, and may accelerate the reorganization of the aberrant olfactory connections responsible for parosmia.
Mechanism of Action in Anosmia/Parosmia
GV23 (Shangxing) — Ethmoidal Stimulation
Point on the frontal midline over the ethmoid; transcutaneous stimulation of the anterior nasal branches of the ethmoid → afferents to the olfactory bulb → stimulated glomerular neuroplasticity.
LI20 (Yingxiang) — Peripheral Olfactory Nerve
Near the nasal foramen; stimulation of olfactory nerve fibers (cranial nerve I) at the level of the olfactory mucosa → VEGF ↑ in the olfactory epithelium → angiogenesis and trophic support to neural cells.
NGF and BDNF — Olfactory Neurotrophins
Acupuncture raises NGF (nerve growth factor) and BDNF (brain-derived neurotrophic factor) locally → support for the survival and regeneration of bipolar olfactory neurons.
ST36 + LI4 — Reduction of Neuroinflammation
Systemic reduction of IL-6 and TNF-α → less neuroinflammation of the olfactory bulb → more favorable environment for reorganization of glomerular connections and resolution of parosmia.
GV20 — Modulation of the Central Olfactory Bulb
GV20 (Baihui) activates the prefrontal cortex and limbic system → modulation of central processing of olfactory information in the piriform cortex → reduction of perceptual distortions.
Scientific Evidence
Post-COVID-19 RCT (n=72) — Preliminary Evidence
2022 Study — Acupuncture + Olfactory Training (n=58)
Modern Approach: Integrative Medical Acupuncture
CLINICAL PROTOCOL IN POST-VIRAL ANOSMIA/PAROSMIA
| PARAMETER | SPECIFICATION | RATIONALE |
|---|---|---|
| Main points | GV23 + LI20 + ST3 bilateral | Ethmoidal and peripheral olfactory stimulation |
| Systemic points | LI4 + ST36 + GV20 | Anti-inflammatory + central olfactory bulb |
| Frequency | 2 sessions/week for 8–12 weeks | Neuronal regeneration requires time |
| Mandatory combination | Olfactory training 2x/day concurrent | Synergy between acupuncture and neuroplasticity |
| Monitoring | UPSIT or Sniffin Sticks every 4 weeks | Objective assessment of recovery |
| Nasal vitamin A | Add as trophic adjuvant | Potentiates regeneration of the epithelium |
When to See a Medical Acupuncturist
Preferred Indication
- Post-COVID-19 anosmia lasting >3 months
- Parosmia with impact on eating and quality of life
- Patients undergoing olfactory training without progress
- Post-influenza with persistent anosmia
Investigate First
- Cranial MRI if unilateral anosmia or after trauma
- Nasoendoscopy to rule out polyps or mass
- Anosmia with absent puberty: genetics (Kallmann)
- Anosmia + other neurological deficits: neurology
Frequently Asked Questions
Frequently Asked Questions
In patients with short-duration post-viral anosmia (less than 6 months), recovery — including spontaneous — can be significant, and olfactory training, with or without acupuncture, is the foundation of treatment. In long-duration cases, recovery tends to be partial. Outcomes vary considerably and there is no guarantee of complete recovery.
Yes, frequently. Parosmia is a sign that nerve regeneration is occurring — neurons reconnecting to the olfactory bulb. The intensity may temporarily increase in the first weeks of treatment before reducing, as connections become more precise. This phenomenon is expected and does not indicate real worsening.
On average 4 to 6 weeks of combined treatment (acupuncture + olfactory training). The UPSIT shows measurable improvement before the patient subjectively perceives it. Younger patients and those with shorter anosmia duration respond more quickly.
Yes — it is essential. Olfactory training is the intervention with the best evidence support and must be maintained. Acupuncture has been investigated as an adjuvant, possibly acting via neurotrophic support (BDNF, NGF) and vascular modulation — hypotheses still under investigation. They are complementary approaches, not alternatives.