I smell bad what should i do

Smell disorders - causes and risks

According to their causes, olfactory disorders are initially divided into sinunasal and non-sinunasal.

Sinunasal olfactory disorders

In sinunasal olfactory disorders, the inhaled air is hindered on its way to the olfactory mucous membrane - so fragrances cannot trigger odor perception. This can be caused by inflammation in the area of ​​the nose or sinuses. This inflammation can be infectious, for example in the course of a recurring infection.

However, the inflammation can also be non-infectious. In these cases, a distinction is made between anatomical and non-anatomical causes. The former include nasal polyps or curvatures of the nasal septum. These anatomical features impede nasal breathing. Non-anatomical causes are swelling of the mucous membranes in the nose or paranasal sinuses as a result of allergies, irritation or as a side effect of medication.

Hormonal changes, for example in the course of pregnancy, or in brain tumors that produce hormones, can also be considered as triggers for sinunasal olfactory disorders.

Sinunasal olfactory disorders usually disappear again after the underlying disease or cause has been eliminated (see also prognosis).

Non-sinunasal olfactory disorders

In the case of non-sinunasal olfactory disorders, the cause lies in damage to the olfactory system itself. This can be caused by different triggers.


Common triggers of non-sinunasal olfactory disorders are skull injuries from a blow to the head or a fall. As a result of such traumatic brain injuries, olfactory nerves can tear off in whole or in part. Bruising and bleeding can also occur in areas of the brain that are responsible for the perception and processing of olfactory stimuli. Trauma usually causes a sudden impairment or a sudden total loss of the ability to smell.

Smell disorders caused by traumatic brain injuries only regress in rare cases - even if the injured or torn olfactory nerves grow back again (see also prognosis).

Toxins and pollutants

Acute or chronic toxic damage to the olfactory mucosa, for example from formaldehyde, tobacco smoke, pesticides, carbon monoxide (CO) or cocaine, can cause an olfactory disorder. Smell disorders can also occur in the context of radiation therapy for cancer therapy. The extent of the olfactory disorder depends on the dose of the poison or pollutant and the duration of its impact on the olfactory mucous membrane.

Virus infections

Viral infections of the upper respiratory tract (e.g. corona infections with the SARS-CoV-2) can also hide behind an olfactory disorder. The infection can damage or even destroy the olfactory nerves. Odor disorders after virus infections are usually associated with an altered perception of smell (parosmia). In about a third of those affected, the olfactory ability improves again within six months.

Other underlying diseases

In addition to viral infections, a number of other diseases can damage or completely destroy the ability to smell. These include neuronal diseases such as Alzheimer's dementia, Parkinson's disease and multiple sclerosis. They cause nerve cells to die in different areas of the brain. If this happens in areas that are important for smelling, the ability to smell can be destroyed or disturbed. In Parkinson's patients, for example, there is a deterioration in olfactory ability six years before the first motor symptoms appear.

Type 2 diabetes, hypothyroidism or epilepsy can also be associated with olfactory disorders. This also applies to depression and schizophrenic psychoses as well as kidney and liver diseases.

Side effects of medication

Medicines that can cause olfactory disorders include: antibiotics such as amicacin, chemotherapy drugs such as methotrexate, antihypertensive drugs such as nifedipine, and pain relievers such as morphine. When the respective medication is discontinued, the olfactory disorders also disappear again.


With advancing age, the olfactory ability decreases due to physiological reasons. Odor disorders in older people can also indicate Parkinson's disease or Alzheimer's dementia.

Hereditary factors

In some patients, the olfactory disorders are innate - so they have not been able to smell in their entire life. The amazing thing is that this disorder is usually not noticed until the age of 10. One of the causes of congenital olfactory disorders can be the underdevelopment or the complete absence of the olfactory bulb (olfactory bulb). This phenomenon occurs, for example, in the so-called Kallmann syndrome. This is an embryonic malformation in which the gonads - testes or ovaries - of the affected newborn are underdeveloped.