Do surgical masks restrict your sense of smell?

By now, it’s a well-known fact that surgical masks are an extremely necessary item in the United States and the rest of the world, with hospitals having to buy them in bulk and wholesale to protect their workers from COVID-19. Along with other medical supplies, like face shields, KN95 masks, N95 masks, and gloves, they have become a first necessity in most of these facilities.

However, it’s been widely reported that COVID-19 could cause a loss of smell. So, could a surgical mask interfere with a diagnosis by restricting the sense of smell? Let’s analyze a study performed to answer this question.

What are surgical masks?

Surgical masks are one of the most widely recognizable face masks in the healthcare field, at least in the USA. They’re mostly used by doctors, nurses, and dentists during procedures, considered the best protection the professional can have for themselves and to avoid contamination of the patient.

These masks form a physical barrier with their fluid-repellent outer layer that prevent liquids from penetrating the mask and being in contact with the wearer. Additionally, their inner layer absorbs moisture from the respiratory droplets the wearer releases, preventing them from reaching the environment and contaminating the patient.

The middle layer of these masks is a filtering one, but they can only filter out large particles, like bacteria. For virus protection, the preferred face mask is the N95 mask, with a popular 3M N95 mask model used in the field being the 3M 1860, and not the 3M 8511 or the 3M 8210, which have industrial uses. Aside from having antiviral properties, these masks can also filter out dust and smoke, among other airborne particles.

Do surgical masks restrict your sense of smell?

It’s a commonly known fact that COVID-19 sometimes comes with a curious symptom: the loss of smell. It’s been determined that 5 to 85% of the patients with this illness report this symptom, and therefore, this question is of great importance. To correctly assess olfaction is important to detect patients who are seemingly asymptomatic and isolate them to prevent more transmission.

The study we’ll be discussing in this article explains that only psychophysical measurements of olfaction can be used as a quantitative criteria to diagnose an olfactory deficit. However, we know COVID-19 is transmitted through respiratory droplets, and therefore the evaluator has to be protected by putting a face mask on the patient.

The effects of wearing different types of face masks on the results of these psychophysical tests is unknown, so a study was performed on a total of 30 people. 20 of them had a normal smell, and 10 of them had an olfactory deficit. In the first group, they were around 27 years old and were distributed equally between males and females, while the second group had an average age of 56 years old and consisted of 7 females and 3 males.

To assess odor identification and sensitivity they used a Sniffin’ Sticks test on people using and not using both surgical masks and N95 respirators. These tests use a felt-tip pen with an odor, and people have to recognize the smell or the intensity.

With the surgical masks, people were put through two identification tests, one with and one without the mask, and two sensitivity tests, one with and one without the mask. They were also equally and randomly divided into two separate groups and they had to go through the tests with the mask on, after which they were given a five minute break to verbally rate the intensity of that odor in a scale that goes from 0 to 10. With N95 masks they did the same experiment.

The results with surgical masks concluded that they do reduce odor sensitivity but not identification, and that normosmic patients (those with a normal sense of smell) and hypoxemic patients (those with a reduced sense of smell) had a similar pattern of olfactory changes with the mask on. The intensity ratings decreased significantly with the surgical mask on.

They concluded that the results could suggest that wearing a surgical mask could reduce the odor sensitivity and intensity ratings. Even though the odor molecules were small enough to pass through the mask’s filter, this decrease in the detection of odor could be due to a reduced airflow. This can be more significant in subtle odors.

Odor identification, on the other hand, showed no significant change with and without the mask, even when the intensity of the odor decreased with the masks on. From a practical point of view, as the study explains, the results suggest that odor identification can still be possible with the mask on.

The results with N95 masks were a little different, where odor identification was affected. Therefore, another conclusion they reached was that N95 masks could be used as a model for anosmia, which is the complete loss of smell, and surgical masks as a model of hyposmia, which is the practical loss or reduced sense of smell, in other experiments about olfactory sensibility.

The main conclusion they reached was that wearing both masks could cause a problem at the moment of detecting one of the most common symptoms of COVID-19, which is the loss of the sense of smell.

Since we’re talking about the use of surgical masks, we want to take this opportunity to remind our readers that healthcare settings are high risk environments where medical-grade masks like surgical masks and others are used for protection. In the general public, reusable cloth masks are recommended for both kids and adults in combination with social distancing measures. They can be easily found for sale online in varying sizes. 

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