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No, wearing a mask doesn’t have any negative health effects

Aside from being mildly uncomfortable when they're worn for extended periods, health experts say the claims circulating on social media about the potential harmful effects of wearing face masks are not true.

With masks now required in Dallas County and in many places across the country, misinformation has spread about their effectiveness in the fight against COVID-19.

Viral posts on social media in recent weeks have claimed that masks can have harmful effects, including depriving a person’s body of oxygen, causing a person to breathe dangerous levels of exhaled carbon dioxide or weaken a person’s immune system.

It’s true that public health experts say some individuals shouldn’t wear masks — including children under 2, people who have health problems that cause breathing difficulties, and people who cannot remove masks on their own.

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But health experts say that aside from being mildly uncomfortable when they’re worn for extended periods, masks don’t cause illnesses. Here’s what you need to know.

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Wearing a mask does not reduce your body’s oxygen level

Some posts have claimed that masks reduce the level of oxygen in a person’s body, causing hypoxemia (low oxygen levels in the blood) or hypoxia (low oxygen levels in the body’s tissues).

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Those conditions can be serious, causing shortness of breath, coughing, fast or slow heart rate, rapid breathing, sweating, wheezing or changes in skin color. Treatment usually requires hospitalization, and in severe cases, people may need to go on a ventilator or other machine to help them breathe, health experts say.

But masks aren’t likely to have those effects on wearers.

A mask “will add some resistance to the breathing process, meaning it may feel like it takes a bit more work to take a breath, but it won’t materially change the makeup of air that comes through the mask,” virologist Angela Rasmussen, a research scientist at Columbia University, told PolitiFact.

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And though wearing a mask may be uncomfortable, that’s only because people aren’t used to wearing them — not because they are having a negative impact on a person’s health.

“Thin paper or cloth masks will not lead to hypoxia,” Keith Neal, an emeritus professor of the epidemiology of infectious diseases at the University of Nottingham, told BBC. “Surgeons operate for hours wearing them. They don’t get these problems.”

According to the Mayo Clinic, the normal amount of oxygen in a person’s blood is between 95% and 100% and anything under 90% is considered low.

Since this claim that masks cause low oxygen levels has circulated social media, doctors and other health experts have posted photos of themselves wearing a mask and using a pulse oximeter, showing that masks don’t have this effect.

Masks don’t cause carbon dioxide toxicity

Another claim in the viral posts is that masks can cause hypercapnia, or elevated levels of carbon dioxide in the blood, caused by breathing in air that was previously exhaled through the mask.

Mild to moderate cases of the condition can cause shortness of breath, headaches, fatigue, delirium or confusion. More severe cases can cause hand tremors, muscle jerks and seizures, health experts say. But the problem is likely to be caused by underlying or other conditions, including hypothermia, nervous system or metabolic disorders, sleep apnea or strokes, health experts say.

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The Centers for Disease Control and Prevention told Reuters that though it is possible for some carbon dioxide to build up in a mask, it would most likely be at a level that would be unnoticeable to the person wearing it.

“The CO2 will slowly build up in the mask over time,” a representative with the CDC told Reuters. “However, the level of CO2 likely to build up in the mask is mostly tolerable to people exposed to it. You might get a headache, but you most likely [would] not suffer the symptoms observed at much higher levels of CO2. The mask can become uncomfortable for a variety of reasons, including a sensitivity to CO2, and the person will be motivated to remove the mask. It is unlikely that wearing a mask will cause hypercapnia.”

Surgical masks are porous and allow carbon dioxide molecules to flow through them. Fabric masks, which the CDC has encouraged using are even more porous. Because cloth and surgical masks often have gaps between a person’s skin and the mask, any additional carbon dioxide would escape, health experts say.

“It has to be a pretty high concentration to be capable of causing harm,” Bill Carroll, an adjunct professor of chemistry at Indiana University Bloomington, told Health. “CO2 is present in the atmosphere at a level of about 0.04%. It is dangerous in an atmosphere when it is greater than about 10%.”

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Some studies have found that health-care providers, who wear heavier duty personal protective equipment, including N95 respirators, for longer periods of time, may experience headaches but not the more extreme symptoms of hypercapnia.

Wearing a mask doesn’t weaken your immune system

Some social media posts have claimed wearing a mask will weaken a person’s immune system because a mask stops other particles from getting into the body, making it unable to fight off diseases it’s used to because your immune system may no longer “remember” them.

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Masks do not stop the person wearing them from breathing in infectious particles. Instead, they create a barrier for infectious particles the person is exhaling. The reason public officials and health experts have stressed wearing masks is because people could be spreading the disease before they begin showing symptoms. The idea is that if everyone wears a mask, everyone is helping to protect each other.

Health experts also say that the claim of reduced resistance is false because infectious particles enter your body in other ways, not just through your mouth.

“Most food, for example, unless made under exceptionally clean conditions or sterilized, contains some microbes,” Dr. Victoria Forster, a postdoctoral fellow at The Hospital for Sick Children in Toronto, Canada, wrote in Forbes. “The same is true for both tap water and bottled water, the latter which can have even more bacteria in it. Many people do also not religiously wash their hands before eating, transferring a ton of microbes from their environment, directly into their bodies. A 10-second kiss with your significant other will also transfer 80 million bacteria from one mouth to another.”

Other health experts say that even shelter-in-place orders that last several weeks won’t drastically alter a person’s immune system, because activities such as going to the grocery store or taking a walk outside expose the body to bacteria and other particles enough to keep the immune system healthy.

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