When you perceive the scent of leather, but no leather object is nearby, you are experiencing phantosmia, a form of olfactory hallucination. This phenomenon causes a person to detect an odor that is not actually present in the environment. Phantosmia can manifest as a phantom smell that is either pleasant or, more commonly, unpleasant, and it can occur in one or both nostrils. Detecting an odor like leather signals that the olfactory system, which includes the nose and the brain, is misfiring or misinterpreting information. Causes range from simple environmental factors to complex neurological conditions.
Environmental and Temporary Triggers
Sometimes, the phantom smell of leather is not a medical issue but a temporary confusion of the olfactory system caused by external factors. A strong olfactory memory can be recalled without the source present, especially if you recently encountered a distinctive leather scent. The brain’s association between a smell and a memory can cause this transient detection.
Extreme fatigue or severe dehydration can momentarily confuse the sense of smell, leading to a brief phantosmia event. Dry air can also irritate the delicate tissues inside the nose, known as the olfactory epithelium. This irritation may result in the misfiring of signals, causing a transient phantom odor before the system resets.
Nasal and Sinus Conditions
More persistent phantom smells often originate from physical issues within the nose and sinuses, affecting the peripheral olfactory system. Conditions that cause inflammation near the nerve endings can distort or create phantom smells.
Chronic sinusitis, which is long-term inflammation of the sinuses, can cause swelling that disrupts the function of the olfactory nerve endings. Similarly, nasal polyps, which are soft, noncancerous growths, can physically interfere with the transmission of odor signals. Both conditions can lead to misfiring of the olfactory sensory neurons, resulting in the perception of a smell that is not actually there.
Upper respiratory infections (viral or bacterial) are common causes of phantosmia because they induce significant inflammation in the nasal passages. This inflammation can damage the olfactory neurons or irritate them into sending incorrect signals to the brain. Once the infection resolves, the phantom smell often disappears, but sometimes the damage can lead to longer-lasting phantosmia.
Neurological and Central Nervous System Causes
When the cause of a phantom smell does not lie in the nose, the issue often relates to how the brain processes scent information, involving the central nervous system. Since the sensation of smell is interpreted in the brain’s temporal lobe, any disruption there can cause an olfactory hallucination, known as central phantosmia.
One specific neurological cause is an olfactory aura, which is a type of focal seizure originating in the temporal lobe. The aura is the initial symptom of a seizure and can manifest as a distinct, repetitive phantom smell.
Head trauma, such as a concussion, can also disrupt the neural pathways connecting the nose to the brain, leading to long-term phantosmia. The impact can damage the olfactory bulb or the cortex where signals are interpreted, causing the brain to generate a phantom odor. Migraines can sometimes be preceded or accompanied by olfactory auras, temporarily causing the perception of a phantom smell. In rare instances, a brain lesion or tumor affecting the olfactory bulb or temporal lobe can cause persistent phantosmia by physically interfering with the neural circuits responsible for smell perception.
Seeking Diagnosis and Treatment
A persistent phantom smell, especially one that is sudden, worsening, or accompanied by other symptoms, warrants a visit to a healthcare professional. You should seek prompt medical attention if the phantom smell is accompanied by severe headaches, vision changes, or signs of a seizure.
The diagnostic path often begins with a primary care provider who may refer you to a specialist such as an otolaryngologist, also known as an ear, nose, and throat (ENT) doctor. An ENT specialist can examine the nasal passages for physical issues like polyps, inflammation, or signs of chronic infection. If a neurological cause is suspected, a referral to a neurologist may follow, who can perform tests to check the central nervous system.
Diagnostic imaging, such as a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan, may be used to rule out underlying structural causes in the sinuses or the brain. Treatment focuses entirely on the underlying cause identified during the diagnosis.
For phantosmia caused by sinus issues, treatment may involve antibiotics to clear an infection or nasal steroids to reduce inflammation. If the phantom smell is linked to a neurological condition like seizures, anti-seizure medication may be prescribed to control the electrical misfiring in the brain. In many cases, phantosmia may resolve on its own once the underlying issue is addressed.