Blood Smell in Nose Without Bleeding: Is Parosmia the Cause?

Damage to your olfactory senses can lead to parosmia, a condition that alters how you perceive odors. If you’ve ever wondered, Why do I smell blood in my nose when there is none, this distorted sense of smell may be one possible explanation. Parosmia can develop after a head injury, bacterial infection, or as a side effect of cancer treatment.

Parosmia is the medical term for disorders that distort your sense of smell. People with this condition may notice a reduced intensity of scents, meaning they can’t fully perceive the range of smells around them. In other cases, everyday odors may suddenly seem unpleasant, metallic, or similar to the scent of blood, even when no bleeding is present.

At times, parosmia causes familiar smells to become overpowering and offensive. This can be distressing, particularly if you’re unsure why certain odors now seem foul or unusual.

Parosmia is sometimes mistaken for phantosmia. However, phantosmia refers to detecting a “phantom” smell when no odor source exists at all. With parosmia, there is an actual smell present — it simply smells “wrong.” For instance, the comforting aroma of freshly baked bread might instead seem rotten or excessively pungent.

Individuals experience parosmia for a variety of reasons. In severe cases, exposure to strong, distorted smells can even trigger nausea or physical discomfort. Understanding how smell disorders work can help clarify unusual experiences, including concerns like What does blood smell like in your nose and why certain scents resemble blood when none is present.

Symptoms of parosmia

Many cases of parosmia become noticeable after recovery from an infection. The intensity of symptoms varies widely from person to person.

If you have parosmia, the most prominent symptom is the persistent perception of a foul or distorted odor, especially around food. You may also struggle to identify or distinguish certain smells in your surroundings due to damage affecting your olfactory neurons.

Scents that once seemed pleasant may now feel overwhelming and intolerable. Attempting to eat foods that smell unpleasant to you can lead to nausea or a loss of appetite. This altered sensory experience may prompt people to search for answers to questions like “Why do I smell blood in my nose when there is none?” particularly when the odor resembles something metallic or bloody.

Causes of parosmia

Parosmia typically develops after the neurons responsible for detecting smells — known as olfactory senses — are damaged by a virus or another medical condition. These neurons line the nasal cavity and send chemical scent information to the brain. When they are harmed, the brain may misinterpret odors.

The olfactory bulbs, located beneath the front part of the brain, receive signals from these neurons and help your brain categorize smells as pleasant, appetizing, neutral, or foul. Injury to these structures can disrupt normal smell processing and contribute to parosmia.

Head injury or brain trauma

Traumatic brain injury (TBI) has been associated with olfactory impairment. The extent and duration of smell disturbance depend on the severity of the injury. A review of medical literature indicates that parosmia symptoms following a TBI are relatively common.

TBI can also cause a loss of smell due to shearing of the olfactory nerve fibers at the cribriform plate. Seizure-related brain trauma may similarly damage these pathways, resulting in distorted smell perception.

Bacterial or viral infection

Upper respiratory infections are a frequent cause of parosmia. Viruses and colds can damage olfactory neurons, particularly in older adults.

In a 2005 study of 56 people with parosmia, just over 40 percent reported having an upper respiratory infection that they believed was linked to the onset of their symptoms. Post-viral smell changes may include metallic or blood-like odors, sometimes accompanied by symptoms such as Smelling blood in nose and headache.

Smoking and chemical exposure

Smoking cigarettes exposes your olfactory system to toxins and irritants that can impair smell function over time. Chronic exposure may increase the likelihood of developing parosmia.

Similarly, repeated contact with toxic chemicals or high levels of air pollution can damage olfactory tissues, contributing to distorted smell perception.

Cancer treatment side effect

Radiation therapy and chemotherapy are known to affect the senses of taste and smell, sometimes leading to parosmia.

A 2016 review found that 86 percent of cancer patients experienced alterations in smell and taste during treatment. In one case study from 2006, this side effect contributed to weight loss and malnutrition because food aversions developed as a result of parosmia.

Neurological conditions

An early symptom of Alzheimer’s disease and Parkinson’s disease can be a diminished sense of smell. Lewy body dementia and Huntington’s disease may also interfere with accurate odor detection.

Tumors

Tumors affecting the olfactory bulbs, frontal cortex, or sinus cavities can lead to changes in smell perception. Although it is uncommon for a tumor to directly cause parosmia, smell disturbances may occur.

More frequently, individuals with tumors experience phantosmia — detecting a smell that is not present — due to tumor-related stimulation of the olfactory system.

COVID-19 infection

COVID-19 has been widely associated with anosmia, or loss of smell. However, some individuals develop parosmia during recovery from the viral infection. Researchers believe the virus may alter the olfactory system in ways that cause lingering distortions in smell.

One 2021 study described two adults recovering from COVID-19 who reported new smell distortions. A 28-year-old male noticed a burnt rubber odor 87 days after illness-related anosmia. A 32-year-old female perceived onions 72 days after infection.

These reports suggest parosmia may represent a possible long-term complication of COVID-19. Researchers involved in the study note that COVID-19–related parosmia is considered rare, and other medical professionals indicate it may signal gradual recovery of the olfactory system.

Because research on the long-term effects of COVID-19 is ongoing, understanding of its impact on smell continues to evolve. For some people, distorted smells — including metallic or blood-like scents — can make eating and daily life more challenging. Discussing olfactory retraining with your healthcare provider may be beneficial.

Diagnosis of parosmia

An otolaryngologist, or ear-nose-throat (ENT) specialist, can diagnose parosmia. During evaluation, the doctor may present various substances and ask you to describe and rate their odors.

A commonly used assessment involves a “scratch and sniff” test booklet containing scented beads that you evaluate under medical supervision.

Your doctor may also ask about:

• family history of cancer or neurological conditions
• recent infections
• lifestyle factors such as smoking
• current medications

If a neurological disorder or cancer is suspected as an underlying cause, further testing may be recommended, including:

• sinus CT
• biopsy of the sinus region
• an MRI

Treating parosmia

In some cases, parosmia can be managed successfully. If it stems from environmental exposures, medication, cancer treatment, or smoking, smell function may improve once the trigger is removed.

Surgery may be necessary if nasal obstructions such as polyps or tumors are contributing to the problem.

Treatments that have been explored include:

• zinc
• vitamin A
• antibiotics

Additional research and case studies are required to confirm whether these treatments are more effective than placebo.

If parosmia persists and affects appetite or body weight, olfactory training therapy — often called “smell training” — may help. This technique involves deliberately smelling four different types of odors up to 15 seconds at a time, twice daily, for several months. Consistency is essential for potential improvement.

Consult your doctor to determine the most appropriate treatment approach for your specific condition.

Recovery from parosmia

Parosmia is often temporary. Over time, olfactory neurons may regenerate. In up to 60 percent of infection-related cases, normal smell function returned in the years following onset.

Recovery timelines depend on the underlying cause and chosen treatment. If your symptoms are linked to a virus or infection, your sense of smell may gradually normalize without intervention. Olfactory training may support this process, although visible improvement can take several months.

The takeaway

Parosmia is frequently traced to infection or brain trauma. When triggered by medication, chemical exposure, or smoking, it often improves after the underlying factor is eliminated.

Less commonly, parosmia may be linked to a sinus polyp, brain tumor, or serve as an early indicator of certain neurological conditions.

Age, sex, and baseline smell ability can all influence long-term outlook. If you notice persistent changes in how odors smell — especially if you find yourself repeatedly asking, “Why do I smell blood in my nose when there is none?” — seek medical evaluation to determine the cause and appropriate next steps.