There has been a raging argument from the beginning of the pandemic over whether masks effectively prevent coronavirus infections. This post has nothing to do with the effectiveness of masks preventing Covid-19. As far as that score goes, you should do what you think is right for you, and you should not break the law. If you are interested in whether I think masks are effective against Covid-19, click here and here. 

Now dissenters claim masks are unhealthy for you, and a few have mentioned that they cause something called mask mouth. I had never heard of it, even though I am a dentist, so I did some digging. 

The definition of Mask mouth is an increase of inflammation and tooth decay due to the recent mask mandates. (1) I personally never blamed masks for anything mouth-related. Initially, I saw an increase in plaque accumulation, gingivitis, tooth decay, and other dental infections, but I have since found things back to normal. My logical conclusion is that people missed cleanings and other dental work due to office closures, making their oral health suffer. 

But the proponents of mask mouth claim that the masks cause us to mouth breathe, which is a known risk factor for oral problems. I searched the literature and could find nothing to back this claim up. The Colgate website claims "disrupted breathing patterns" result from mask-wearing and cites this study. The research states that anxiety, headaches, increased heart rate, confusion, and fatigue can result from mask-wearing. I won't disagree. Nowhere does it claim mouth breathing results from mask-wearing. But Colgate does, and I can tell you that they did not get their information from the article they cited.  

Mouth-breathing may be a legitimate problem with masks; I have heard so from staff, so please let me know in the comments if you breathe through your mouth when you wear your mask. Maybe I can put the numbers together to see if there is a legitimate concern.

Colgate also claims that dehydration is also a problem when wearing masks. Dehydration leads to dry mouths. Dry mouths are a risk factor for dental problems, but no literature supports mask-wearers are prone to dry mouths or don't drink enough water. 

Colgate also claims that when you wear a mask, you trap more carbon dioxide in your mouth than usual. They say it can increase the mouth's acidity, which might put you at risk for decay, infections, or inflammatory conditions like gum disease. They cite this study to back up their claim. The study claims that masks can cause both higher and lower CO2 levels, depending on the mask type. They are careful to state that the concentrations they found in mask-wearers have no toxicological effect. Nowhere do they claim that oral acidity rises to the level that it leads to decay—shame on Colgate. You would think they want you to purchase more toothpaste! 

The Covid issue aside, there are a few studies on masks and health in general; some say they cause problems, and others say they are okay:

In one study, nurses reported feeling more short of breath, headache, lightheadedness, perceived exertion, and impeded communication the longer they wore masks. None of the symptoms were medically relevant; they were merely unpleasant. (2)

Another study showed masks have a marked adverse impact on power output, oxygen uptake, and lung function. Furthermore, the subjects perceived them as being very uncomfortable. (3)

This study shows that masks do not affect arterial oxygen saturation, tissue oxygenation index, rating of perceived exertion, or heart rate. (4)

Psychology Today has noted that masks can cause anxiety. (5) I don't feel stress wearing a mask, but I fear judgment when it is unclear whether I need one. For instance, on a hike where the law in my area says I don't need one, the people I pass on the trail are wearing them and turning away as if I am a leper. 

For people with hearing difficulties, mouth coverings present significant problems. Even with everyday communication, having a mask on can present a communication barrier, especially when attempting to have a deep, meaningful conversation. (6)

Adverse skin reactions with masks occur in 54.5% of wearers; acne was the most frequent at 39.9%, rashes were next with 18.4%, and lastly, itching occurred in 15.6%. Surgical masks were worse than cloth masks. (7)

My 35 years of mask-wearing tell me that surgical and cloth masks do not cause significant health problems for me under most circumstances other than the bother and discomfort after prolonged wear, on hot days, or with higher physical exertion. They are more challenging for me to tolerate now because I have one on from about 7:15 AM until 5:00 PM continually (except for quick changes). But I manage. Others may not be so fortunate. For instance, my wife had asthma, and the mask is difficult for her to wear for any length of time. If you are hard of hearing, have skin rashes, or any other issues I listed, I feel your pain. One thing seems certain to me: the science does not support that masks cause mask mouth. If you think your oral health is worse, don't be so quick to blame your mask. You should schedule an appointment with your dentist to determine the cause.