The experience of smelling strange or unpleasant odors when sick is more common than many people realize. This phenomenon, known medically as dysosmia, results from disruptions to the body's delicate olfactory system. It’s a sensory quirk that can range from a minor annoyance to a deeply unsettling issue, often related to viral or bacterial infections that temporarily damage the sense of smell.
The Olfactory System and Illness
Your sense of smell relies on a complex chain of events. Odor molecules in the air enter your nose and are detected by specialized olfactory sensory neurons located high in your nasal cavity. These neurons send signals to the olfactory bulb, a part of the brain that processes smell information. During an illness, this process can be disrupted in several ways:
- Inflammation and Obstruction: Infections like the common cold, flu, and sinusitis cause swelling and excess mucus in your nasal passages. This physical blockage prevents odor molecules from reaching the olfactory neurons, dulling your sense of smell. As a result, your brain may attempt to fill in the missing information, leading to distorted perceptions.
- Neural Damage: Certain viruses can directly damage the delicate olfactory sensory neurons or the supporting cells within the nasal cavity. While these cells can eventually regenerate, the healing process is often imperfect. As the nerves attempt to rewire themselves, the signals they send to the brain can become jumbled, causing a familiar scent to register as something entirely different and often unpleasant.
- Immune System Response: Research suggests that the body's immune response itself can alter our perception of smells. During an infection, the immune system releases chemicals that could potentially affect the way we detect odors, acting as a kind of biological early warning system.
Key Causes for Altered Smell When Sick
Infections and other health issues are the most frequent culprits behind these strange olfactory experiences. The most common causes include:
- Viral Infections: The common cold, influenza, and, most notably, COVID-19 are all known to cause temporary or long-term issues with the sense of smell. In many cases, patients first experience a loss of smell (anosmia), followed by distorted smells (parosmia) as they recover.
- Sinus Infections: Both acute and chronic sinusitis can cause fluid and inflammation that lead to foul-smelling mucus and distorted odors. A lingering, rotten smell in the nose is a classic symptom of a bacterial sinus infection.
- Nasal Polyps: These noncancerous growths in the nasal passages or sinuses can create blockages that distort or decrease your sense of smell. They can also trap fluid, leading to foul odors.
- Dental Issues: Poor oral hygiene, tooth decay, or even tonsil stones can cause foul-smelling bacteria to grow, which can then affect your sense of smell.
Differentiating Parosmia and Phantosmia
Dysosmia can manifest in two primary ways: parosmia and phantosmia. While often confused, they describe distinct experiences:
| Feature | Parosmia (Distorted Smell) | Phantosmia (Phantom Smell) |
|---|---|---|
| Scent Source | A real-world odor is present. | No external odor is present. |
| Perception | A familiar smell is perceived as something different, and often unpleasant. | An odor is detected when there is none. |
| Common Description | Coffee smells like gasoline or burnt food; meat smells rotten; flowers smell like chemicals. | Smelling burnt rubber, chemicals, or garbage that isn't there. |
| Cause | Damage to olfactory receptor neurons, especially during the healing phase after a viral infection. | Can be triggered by infections, head trauma, migraines, or neurological issues. |
| Timing | Often occurs weeks or months into recovery from an illness. | Can be occasional or constant, and may appear during or after an illness. |
The Connection to Specific Illnesses
COVID-19: The pandemic brought widespread awareness to olfactory dysfunction. A significant number of individuals with COVID-19 initially experienced anosmia (loss of smell), and as they began to recover, developed parosmia, with everyday foods and smells becoming unpalatable. This is often considered a sign that the nerves in the olfactory system are regenerating.
Common Cold & Flu: Long before COVID-19, the common cold and flu were known causes of post-viral olfactory loss. The viruses can damage the nasal linings, leading to lingering smell changes. For most people, this resolves with time, but it can sometimes last longer.
Sinusitis: Chronic inflammation from a sinus infection is a frequent cause of distorted smell. The buildup of mucus can affect how odor molecules are processed, and the presence of bacteria can contribute to foul-smelling sensations.
What You Can Do About Distorted Smells
If you are experiencing a weird or distorted smell, the first step is to address the underlying illness. For minor infections like a cold, symptoms will often resolve on their own. For more persistent issues, or in cases of post-viral dysfunction, several strategies can help:
- Olfactory Training: Also known as "smell training," this involves regularly sniffing a set of strong scents, such as rose, eucalyptus, lemon, and cloves, while consciously recalling the correct memory of that smell. This can help retrain the nervous system and is a well-regarded therapy for post-viral smell loss.
- Nasal Rinses: Using a saline nasal spray or sinus rinse can help clear out congestion and excess mucus, which may improve smell perception.
- Lifestyle Adjustments: If certain foods are triggering unpleasant smells, eating simpler, blander meals or eating food at a different temperature can help. Some people find that warmer foods and drinks release more triggering odors, so opting for cold or room-temperature options can be beneficial.
- Avoid Triggers: If you identify specific smells that trigger your parosmia, try to avoid them temporarily. This can be especially helpful with strongly scented items like coffee, onions, or garlic.
When to See a Doctor
While most cases of altered smell are temporary and benign, you should consult a healthcare provider if:
- The symptoms are persistent and do not improve over several weeks.
- You suspect a sinus infection, especially if accompanied by thick, colored mucus.
- You notice additional neurological symptoms, such as headaches, seizures, or vision changes.
- You experience significant weight loss or anxiety due to food aversion caused by the smell distortion.
Conclusion
Smelling a weird smell when you're sick is a well-documented phenomenon, most often caused by the inflammation and damage that viral or bacterial infections inflict on your delicate sense of smell. Whether it’s a phantom odor or a distortion of a familiar one, the experience can be unsettling but is often a temporary side effect of the body's healing process. By understanding the underlying mechanisms and employing simple coping strategies like smell training, you can navigate this sensory disruption and support your body's recovery. For persistent or concerning symptoms, consulting a healthcare professional can help rule out other potential causes and provide further guidance.
