What is the difference between hyposmia and anosmia?

Hyposmia and anosmia are conditions that describe varying degrees of impairment or absence of the ability to detect odors. The fundamental difference lies in the extent of the impairment: hyposmia means a reduction or weakness in the ability to detect odors, where a person can still smell some scents but with less intensity than normal, whereas anosmia is defined as a total loss of the ability to perceive any odors at all [1].

How do these disorders differ in nature?

These conditions are part of chemosensory disorders. In rare cases, some individuals are born without a sense of smell entirely due to a genetic condition known as congenital anosmia [1]. On the other hand, other related disorders may appear, such as parosmia, where there is a distortion in the perception of familiar odors, or phantosmia, which is the sensation of smelling an odor that is not actually present [1]. Since the senses of smell and taste work together, many people who think they have lost their sense of taste later discover they actually suffer from an olfactory disorder, because odors play a pivotal role in perceiving food flavors through the channel that connects the back of the throat to the nose [1] [2].

Underlying causes of olfactory disorders

The causes leading to hyposmia or anosmia vary and are often related to a recent illness or injury. Common causes include [1]:

• Upper respiratory infections, such as colds or sinusitis, which may block nasal passages.
• Aging, as problems with smell tend to increase with age.
• Head or neck injuries.
• Exposure to certain chemicals such as solvents and pesticides.
• Side effects of certain medications, including specific types of antibiotics and antihistamines.
• Abnormal tissue growth inside the nose, such as polyps.
• Health conditions that affect the nervous system, such as Alzheimer's disease or Parkinson's disease.

To learn more about how to manage these conditions, you can read our guide on Olfactory and Taste Disorders: Causes, Diagnosis, and Treatment Options (Arabic).

When should you consult a doctor?

Evaluation by an Ear, Nose, and Throat (ENT) specialist is necessary, especially since the loss of smell can serve as an early warning sign for serious health problems such as diabetes, neurological diseases, or even high blood pressure [1] [2]. The doctor will perform a clinical examination of the ear, nose, and throat and may request specialized smell tests that rely on measuring the accuracy of scent discrimination or detecting the presence of odors [1]. If the cause is a specific medication, the doctor may recommend adjusting the dose or changing it, but medication should never be stopped without direct medical consultation [2]. Remember that the sense of smell acts as a vital safety system that warns you of environmental hazards, such as gas leaks or spoiled food, so neglecting this symptom may affect your general safety and quality of life [1] [2].

Medical references

• Smell Disorders
• Taste Disorders