Work complaints: We’ve all got them. You know, passed over for a raise or promotion, a boss who makes you crazy, co-workers whom you can’t stand. But has a manager ever told you to “put some mustard” on a serious burn?

That is one allegation against McDonald's Corp. from workers who filed 28 health and safety complaints against the fast-food giant in 19 cities on Monday via a union-backed group known as Fast Food Forward or Fight for $15. The group launched a petition on Monday calling on the U.S. Department of Labor to investigate health and safety hazards in the fast-food industry.

Everyone knows that it's no picnic to work at most fast-food restaurants — low pay, lots of evening hours (though often not enough hours per week to make ends meet), limited career prospects. But according to new research pointed out by Fight for $15, some 2.8 million workers were burned on the job this year. That is four out of five fast-food workers.

That survey, released Monday on behalf of the National Council for Occupational Safety and Health, revealed that workers suffer repeated burns, largely due to understaffing and speed requirements. And 36% of workers say they were told to treat burns with mustard, mayonnaise, butter or ketchup.

Brittney Berry, who has worked at a McDonald’s in Chicago since 2011, reportedly told Fight for $15 that she slipped on a wet floor and caught her arm on a hot grill. The result? A severe burn and nerve damage. “The managers told me to put mustard on it, but I ended up having to get rushed to the hospital in an ambulance,” she is quoted as having said.

Here’s the video released by Fight for $15 in conjunction with its complaint. A spokesman for the group said that the McDonald’s workers in the video largely wished to remain anonymous so that they could talk about conditions in the specific stores where they work.

Fight for $15 also has some graphic images of the burns suffered by workers at big corporations.

In a statement, McDonald’s said the company MCD, -1.03% and its franchisees are committed to providing safe working conditions and it will review the safety allegations. “It is important to note that these complaints are part of a larger strategy orchestrated by activists targeting our brand and designed to generate media coverage,” the McDonald’s statement added.

In defense of those McDonald’s managers who recommended mustard therapy for burns, the People’s Pharmacy says cold, cheap yellow mustard does indeed relieve burns if applied after immediate first aid with cold water. Soy sauce also works, they say, though www.natural-homeremedies-for-life.com says salves and butters should never be used as they are usually oil-based. There was no mention of ketchup.

As for third-degree burns? They always require medical attention, doctors say.