7 Causes of Anosmia, or Loss of Smell

In case you’ve never heard of it, anosmia is the partial or complete loss of sense of smell. It’s caused by a variety of mental and physical health conditions.

Anosmia remains a relatively unknown problem, due primarily to a lack of data or studies thoroughly examining the issue. That said, those affected by it know it’s an incredibly frustrating condition. So, what conditions can cause anosmia?

1. Brain Trauma

Our understanding of brain trauma—whether caused by sports injuries, automotive accidents, or something else— continues to build. For those who suffer from a significant brain injury, the symptoms are many and often last for years after the event.

One of these symptoms can be anosmia. Injury to the brain often causes smell loss, which can last for a short or longer period of time. Specifically, damage to the brain’s frontal lobe, where the smell is processed. Direct injury to the nose can also cause loss of smell, though this issue typically resolves itself faster than a brain injury.

2. Respiratory Viral Infection

Anyone who’s suffered a bad cold or flu knows that it can cause a slight or significant loss of smell or anosmia. That’s because these kinds of infections can actually result in damage to the interior lining of the nose and sinuses, making it difficult for a person to detect odors.

Viral infections of the upper respiratory system are particularly problematic in this regard. While they often lead to anosmia, in most cases the result is parosmia or a distorted sense of smell that can cause sufferers to react negatively to typically pleasant smells. This is caused by damage to the olfactory receptor cells. The good news is that effective treatment of the source infection typically leads to positive long-term outcomes.

3. Idiopathic Anosmia

In a surprisingly high number of cases, there is no physical explanation for a patient reporting partial or complete loss of smell, or anosmia. Even after extensive testing—involving blood tests and brain scans—has been performed, it can be difficult to find a physical reason for the emergence of smell loss.

Patients who report loss of smell but demonstrate physical conditions that can explain the development may go on to develop dementia-related problems, including Parkinson’s disease and Alzheimer’s disease. That’s why it’s so important that older adults speak with their physician as soon as anosmia-related issues emerge.

4. Nose or Sinus Trauma

Those who have sustained a significant nose injury— such as a broken nose—know how painful the condition can be, both at the time of the injury and in the weeks that follow.

Aside from pain, another possible side effect of trauma to the nose and sinuses is loss of smell or anosmia. Swelling around the nose and sinuses can cause people to lose their ability to smell, this sense typically returns once the inflammation goes down. It is worth noting, a bad cold, nasal polyps, and seasonal allergies can cause anosmia as well.

5. Congenital Anosmia

A very small percentage of people who suffer from partial or complete loss of smell—about one percent—have what’s known as congenital anosmia. In these cases, people are born without any ability to smell.

It may be related to Kallmann syndrome, a condition that involves insufficient hormone production by the pituitary gland. This is typically related to a brain defect in the hypothalamus that can also involve fertility problems.

6. Dementia

Diseases involving dementia—including Parkinson’s disease and Alzheimer’s disease—can cause anosmia or the partial or complete loss of smell. In fact, it’s possible for anosmia to show itself months or even years before the emergence of Parkinson’s disease or Alzheimer’s disease.

In a way, then, anosmia can be an effective way of detecting dementia-related conditions before they appear. That’s why it’s crucial that adults, and especially older adults, to speak with their doctor if they detect partial or total loss of smell.

7. Other Issues

There are a number of other health conditions that can result in slight or significant loss of smell. For example, some liver and thyroid gland problems can cause patients to experience anosmia. In addition, some diabetics and epileptics can also find that their sense of smell has worsened.

Regardless of their health situation, people who experience any loss of smell—whether slight or significant—should immediately consult their physician. Blood tests, brain scans, and other types of examination can help to determine if the matter is temporary, meaning it may be the result of seasonal allergies, a cold or the flu, or related to something more significant, such as the emergence of a liver, thyroid, or dementia-related condition.


Emily Lockhart

Emily Lockhart is a weight loss expert who specializes in healthy living. She is dedicated to providing health-conscious individuals with the information they need to make great lifestyle choices that will make them look and feel better. In her spare time, Emily teaches Pilates at a local studio and enjoys activities like hiking, rowing and biking.