Mask advocates raged at popular West Coast burger chain In-N-Out after the company banned mask-wearing for employees in five states.

The policy will start Aug. 14, according to a leaked memo, and will affect employees in Nevada, Arizona, Utah, Texas and Colorado. Stores in California and Oregon, which have laws preventing employers from banning masks, are exempt from the new policy.

The In-N-Out memo said the decision was intended to improve customer service by showing off employee's smiles. Exemptions would be given to employees who had a "valid medical note."

Even if approved, the employee must wear "a company-provided N-95 mask," per the memo, unless the employee's doctor says otherwise.

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In-N-Out

In-N-Out's new anti-mask policy upset liberals on Twitter. (Justin Sullivan/Getty Images)

Mask advocates complained about the new policy on social media, and encouraged their followers to contact the company's customer service line to voice their opposition.

Columbia University Irving Medical Center scientist Dr. Lucky Tran, who shared the leaked employee memo on Twitter, slammed the policy as "discriminatory" and "harmful."

"Please remember to call In-N-Out and tell them that their ban on wearing masks is harmful," she tweeted.

 Epidemiologist Dr. Eric-Feigl-Ding also warned others to "avoid" the burger chain.

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People gather in support of continuing the school mask mandate

Some liberals on Twitter raged about In-N-Out's new employee mask policy. (Matt McClain/The Washington Post via Getty Images)

Some Twitter users gave a more blunt response to the mask ban.

Independent journalist Walker Bragman cursed at the burger chain while writing them off as "a weird, culty right-wing company anyway."

"Well, f–k In-N-Out Burger then," he tweeted.

"In-N-Out Burger doesn’t give a s—t if you’ve got an immune compromised family member at home. Or if you yourself are immune compromised," another liberal tweeted. "Triggered by masks. F—k off In-n-Out. I do not care if I go into a business and someone is wearing a mask."

Another Twitter user announced she was "too upset" about the mask policy to put her thoughts into words.

"I wrote 3 different responses and erased them all. I'm too upset to appropriately put my thoughts into words. But I will, because the employees of in-n-out burger deserve our support," she tweeted.

California, In-N-Out's home state, was one of the strictest states in the nation on enforcing masking policies during the COVID-19 pandemic.

In the fall of 2021, the city of San Francisco temporarily shut down an In-N-Out restaurant that refused to follow a mandate forcing customers to prove they were vaccinated against the coronavirus.

In-N-Out did not return a request for comment.

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Fox News' Jeffrey Clark contributed to this report.