A persistent mothball smell with no obvious source usually points to one of two very different explanations: either naphthalene or paradichlorobenzene, the chemicals in actual mothballs, is lingering somewhere in your environment that you haven’t identified, or your brain is generating a smell that isn’t physically there. The second possibility, known as phantosmia, is more common than most people expect and has a surprisingly wide range of triggers. Figuring out which category you fall into changes what you should do about it.
The Smell Might Actually Be There
Before assuming something is wrong with your nose, consider whether the chemical itself is present somewhere nearby. Mothballs work by sublimating, meaning the solid slowly converts to a gas at room temperature. That gas, usually naphthalene, seeps into fabrics, wood, insulation, and drywall, and it can hang around for months or even years after the mothballs themselves are gone. If you’ve moved into an older home, bought vintage furniture, or inherited stored clothing, there’s a good chance you’re inhaling naphthalene residue without realizing the source.
Naphthalene also has sources outside the mothball aisle. It’s a polycyclic aromatic hydrocarbon found in tobacco smoke, vehicle exhaust, certain industrial solvents, and some older roofing materials. Indoors, mothball use is one of the more significant contributors to elevated naphthalene concentrations, but it’s not the only one. If you recently moved, renovated, or opened a long-sealed closet or attic, the mothball smell you’re detecting could be real naphthalene released from materials that absorbed it years ago.
This matters because naphthalene exposure carries genuine health risks. Breathing it in at elevated indoor levels has been linked to respiratory irritation, headaches, and nausea. There’s growing concern about longer-term effects as well, and certain populations, including young children, people with a genetic enzyme deficiency called G6PD deficiency, and pregnant women, face higher vulnerability to naphthalene toxicity.1PubMed Central. Naphthalene Mothballs: Emerging and Recurring Issues and their Relevance to Environmental Health If you can trace the smell to an actual source, ventilation and removal of contaminated materials should be your first priority.
When There’s No Physical Source
If you’ve searched your home thoroughly and there’s genuinely no mothball, no old trunk, no naphthalene source, the smell is likely phantosmia: the perception of an odor that isn’t present. A population-based study of older adults found that roughly one in twenty people experience phantom smells, with women more affected than men.2Oxford University Press. Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults The most commonly reported phantom smell in that study was smoky or burnt, but chemical and acrid odors, including descriptions that overlap with mothballs, are also reported. Many people who experience phantosmia never discover the cause and find that it resolves on its own over weeks to months.
Phantosmia is different from parosmia, where a real smell gets distorted into something unpleasant. With phantosmia, there’s no external trigger at all. Both conditions share some underlying causes, though, and they can occur together. The same study found that people reporting phantom smells were also significantly more likely to have parosmia.2Oxford University Press. Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults
Post-Viral Smell Distortion
If the mothball smell started after a cold, flu, or COVID infection, that’s a strong clue. Viral infections are one of the most common causes of both phantosmia and parosmia. The virus damages the olfactory neurons lining the upper nasal cavity. When those neurons regenerate, they don’t always wire back up correctly, leading to scrambled or phantom odor signals. Think of it like a phone cord plugged into the wrong jack: the signal arrives, but the information it carries is garbled.
COVID brought this phenomenon into sharper focus because of the sheer number of people who lost their sense of smell simultaneously. Studies tracking patients who reported smell loss during acute COVID found that somewhere between 28% and 43% later developed parosmia as their sense of smell returned.3BMJ Medicine. Post-viral olfactory loss and parosmia Research into which specific molecular compounds trigger the distorted perception found that the problem tends to cluster around chemicals with very low odor thresholds, meaning compounds your nose can detect even at tiny concentrations.3BMJ Medicine. Post-viral olfactory loss and parosmia This helps explain why post-viral smell distortion often produces harsh chemical or acrid odors rather than, say, the smell of flowers. Your recovering nose is hypersensitive to certain molecular shapes and misinterpreting them.
The encouraging news is that post-viral smell distortion does tend to improve with time. For most people, the scrambled connections gradually sort themselves out over months, though the timeline varies widely. Smell training, where you deliberately sniff a set of distinct scents for a few minutes twice daily, is the most studied rehabilitation approach and has shown modest benefits in speeding recovery. It won’t provide instant results, but it’s low-risk and easy to try at home.
Sinus Problems and Nasal Inflammation
Chronic rhinosinusitis, which is persistent inflammation of the sinuses lasting at least 12 weeks, is a well-established cause of olfactory dysfunction.4PubMed. Chronic rhinosinusitis and olfactory dysfunction Most people associate sinus issues with reduced smell, but the relationship is messier than that. Inflamed sinuses can produce distorted smells too, particularly when the inflammation affects the olfactory cleft, the narrow passage at the top of the nasal cavity where odor receptors are concentrated. Polyps, chronic infection, or swelling in that area can alter how odor molecules reach and interact with those receptors, producing phantom or distorted perceptions.
If your mothball smell comes and goes with congestion, gets worse when you lean forward, or coincides with sinus pressure, this is worth investigating. An ENT specialist can examine the olfactory cleft with an endoscope and assess whether inflammation or polyps are involved. Treating the underlying sinus disease, whether with nasal corticosteroids, saline irrigation, or in some cases surgery, often improves the smell distortion as well.
Neurological Triggers
Phantom smells can occasionally point to something happening deeper in the brain. The olfactory system is wired directly into the temporal lobe, amygdala, and limbic structures, and abnormal electrical activity in those areas can produce vivid odor perceptions. In epilepsy, these are called olfactory auras, and they often precede other seizure symptoms. A case study documented olfactory auras caused by epileptic activity confined to a small region of the amygdala. The patient experienced recurring putrid odors strong enough to wake him from sleep, driven by brief bursts of abnormal electrical discharge that didn’t spread to other brain areas.5PubMed Central. Olfactory auras caused by a very focal isolated epileptic network in the amygdala The fact that surgical removal of the tiny focus eliminated the phantom smells confirmed that the brain, not the nose, was generating them.
Parkinson’s disease is another neurological condition where phantom smells show up, though the connection is less straightforward. A systematic review found that olfactory hallucinations in Parkinson’s patients were reported in anywhere from less than 1% to about 18% of cases, with women making up a larger proportion of those affected.6MDPI. Phantosmia in Parkinson’s Disease: A Systematic Review of the Phenomenology of Olfactory Hallucinations Parkinson’s is well known to damage the olfactory system early in its course, often before motor symptoms appear, so phantom smells in a person who also notices a diminished sense of smell, tremor, or stiffness deserve a neurological evaluation.
To be clear, a persistent mothball smell is far more likely to be post-viral, sinus-related, or environmental than a sign of epilepsy or Parkinson’s. But if phantom smells are accompanied by other neurological symptoms, such as brief episodes of confusion, involuntary movements, memory changes, or loss of consciousness, those combinations warrant a prompt medical workup.
Medications That Can Alter Smell
Your medicine cabinet is an underappreciated source of phantom smells. A study of U.S. adults found that people taking five or more prescription medications had roughly 70% higher odds of reporting phantom odor perception compared to those on fewer drugs.7PubMed Central. Prescription Medication Use and Phantom Odor Perception Among US Adults Specific classes stood out among older adults: diabetes medications, cholesterol-lowering drugs, and proton pump inhibitors were each associated with roughly 74% to 88% greater odds of phantom smells.7PubMed Central. Prescription Medication Use and Phantom Odor Perception Among US Adults
The mechanism isn’t fully understood. Some of these drugs may directly affect olfactory receptor turnover, while others may alter the mucus environment in the nasal cavity or influence neurotransmitter systems involved in odor processing. Regardless of the how, the practical implication is straightforward: if you started smelling mothballs around the time you began a new medication or changed doses, mention it to your prescriber. Sometimes a dose adjustment or a switch within the same drug class resolves the issue without sacrificing the treatment you need.
Anxiety, Stress, and Olfactory Hallucinations
Most people associate hallucinations with severe psychiatric conditions like schizophrenia, so it can be alarming to hear that anxiety alone can produce phantom smells. But it can. A documented case report described a patient whose sole initial symptom of anxiety disorder was an olfactory hallucination, and the phantom smell preceded the formal anxiety diagnosis by several years. Treatment with anti-anxiety medication resolved the phantom smell.8PubMed Central. First-episode olfactory hallucination in a patient with anxiety disorder: A case report
This doesn’t mean that everyone who smells mothballs has an anxiety disorder, but it does mean that stress and anxiety deserve consideration as contributing factors, especially if the phantom smell intensifies during periods of heightened worry, poor sleep, or emotional distress. The brain’s olfactory processing areas overlap heavily with its emotional centers, so a nervous system running on high alert can misfire in ways that produce sensory experiences with no external input. If you notice the smell worsening during stressful weeks and improving when you’re relaxed, that pattern itself is informative.
Ruling Out Environmental Sources You Might Miss
Before concluding that the problem is in your nose or brain, consider some less obvious environmental sources. Naphthalene and similar volatile organic compounds can accumulate in places that are easy to overlook:
- Wall cavities and attic insulation: Previous homeowners may have placed mothballs inside walls or crawl spaces as pest deterrents, a practice that was once common. The compounds absorb into porous materials and off-gas for years.
- Vintage or secondhand items: Clothing, books, trunks, and upholstered furniture stored with mothballs retain the chemical. A single vintage coat in a closet can make an entire room smell.
- Car interiors: Some people place mothballs in vehicles to deter rodents during storage. The enclosed space concentrates the fumes.
- Adjacent apartments or shared HVAC: In multi-unit buildings, a neighbor’s heavy mothball use can push naphthalene into shared ventilation systems or through gaps in walls and ceilings.
A handheld volatile organic compound meter, available for around $100 from home improvement stores, can help you determine whether there’s actually an elevated chemical level in your environment. If the meter confirms elevated VOCs, the fix is source removal and ventilation. If levels are normal and you still smell mothballs, the phantom smell explanation becomes much more likely.
Clearing Naphthalene From Your Home
If you do find an environmental naphthalene source, getting rid of the smell requires more than just opening a window, though ventilation is a good first step. Naphthalene is lipophilic, meaning it binds to oily and porous surfaces, so simply airing out a room may not be enough if the chemical has soaked into fabrics or wood.
Start by removing the source itself: any remaining mothballs, contaminated clothing that can’t be laundered, or infused insulation. Washable fabrics should be laundered or dry-cleaned. Hard surfaces can be wiped down with soap and warm water. For persistent contamination in enclosed spaces like closets or attics, running an air purifier with activated carbon filtration can help. Activated carbon works through physical adsorption, trapping the volatile organic compounds on its surface, and is effective for low-molecular-weight chemicals like naphthalene.9PubMed Central. Removal of volatile organic compounds by chemical filters significantly inhibited the development of atopic dermatitis symptoms in mice: potential implications for air-conditioning systems in healthcare environments Standard HEPA filters alone won’t cut it because they capture particles, not gases. You need the activated carbon component specifically.
In severe cases, where mothballs were used extensively inside wall voids or an entire basement, professional remediation may be necessary. Some situations call for removing drywall, replacing insulation, or sealing contaminated surfaces with vapor-barrier coatings. This is uncommon but worth knowing about if you’ve acquired a property with a history of heavy mothball use.
When to See a Doctor
A one-off whiff of mothballs when you open a closet is unremarkable. But a persistent or recurring mothball smell that you can’t trace to an environmental source is worth discussing with a doctor, especially if any of the following apply:
- Recent viral illness: Post-viral phantosmia and parosmia are treatable and may benefit from smell training or other interventions.
- New medications: A temporal link between starting a drug and the onset of phantom smells is an important clue for your prescriber.
- Neurological symptoms: Any combination of phantom smells with confusion, seizure-like episodes, tremor, or memory changes calls for evaluation.
- Emotional distress: If the phantom smell is accompanied by worsening anxiety, intrusive thoughts, or disrupted sleep, addressing the underlying mental health concern may resolve the smell.
- Duration: A phantom smell lasting more than a few weeks without improvement deserves investigation.
Your doctor will likely start with a detailed history and a nasal exam, and may refer you to an ENT specialist or a neurologist depending on the associated symptoms. There’s no single test that diagnoses phantosmia; it’s largely a clinical diagnosis made by ruling out identifiable causes.
Why Treatment Is Tricky
Phantosmia is frustrating to treat in part because the underlying mechanism isn’t always clear. It could originate in the nose, the olfactory nerve, or the brain’s processing centers, and the right treatment depends on where the signal goes wrong. One approach that was tested, applying cocaine topically to the nasal lining to temporarily block olfactory nerve transmission, was evaluated in a small study and showed no long-term benefit for phantosmia patients. The researchers noted this result may suggest that at least some cases of phantosmia stem from a central brain processing issue rather than a peripheral nerve problem.10PubMed. Olfactory cocainization is not an effective long-term treatment for phantosmia
In practice, treatment is usually directed at the suspected underlying cause. Sinus disease gets treated with anti-inflammatory approaches. Post-viral cases get smell training and time. Medication-related phantosmia gets a drug review. Anxiety-related cases may respond to appropriate mental health treatment. And for the subset of people where no clear cause is found, the condition often fluctuates and may eventually fade on its own. Living with phantosmia can be genuinely disruptive, affecting appetite, mood, and quality of life, so if you’re struggling with it, pushing for a thorough workup rather than accepting “it’ll go away eventually” is entirely reasonable.
Occupational and Historical Exposures
People who work in certain industries may have both a heightened awareness of the mothball smell and an actual exposure history that complicates the picture. Naphthalene has been used not only as a domestic moth deterrent but also as a pesticide in agricultural and museum settings, where it was applied to textiles and artifacts to prevent insect damage. Museum workers, textile conservators, and pest-control professionals can accumulate significant exposures over time, particularly through inhalation and dermal contact.11Elsevier. Harmful health effects of pesticides used on museum textile artifacts – overview
What makes occupational exposure relevant to the “why do I keep smelling mothballs” question is that chronic chemical exposure can itself alter olfactory function. People with prolonged naphthalene exposure may develop a heightened sensitivity to the compound, detecting it at concentrations well below what other people notice, or they may develop smell distortion that makes unrelated chemicals register as naphthalene-like. If you’ve worked around mothballs, fumigants, or similar aromatic hydrocarbons, this history is worth mentioning to your doctor. The conversation is different when the nose has been chemically trained to be vigilant for a particular molecule.