Seo Hye Han, a principal dancer with the Boston Ballet, performs the role of Dew Drop in “The Nutcracker” at the Boston Opera House. (Josh Reynolds for The Washington Post)

Her calves are cramping and her back is aching, but if Megan Johnson, a New York City Ballet dancer, peers through her false eyelashes at the first rows of the audience during any given “Nutcracker” performance, she remembers why she’s there.

Standing onstage as a flower in her fluffy pink skirt and rose headpiece, she can see faces in the nearest rows, little children and even grown men who are completely caught up in the ballet. And she sees their joy.

Maybe this is their first ballet, and the tickets are expensive — all this passes through her mind as she stands there, which is a good thing, because if she were to think instead about the painful corns between her toes, or the fact that she’ll be stuck in this exact spot every night for the next several weeks, sometimes twice a day, year after year, another “Nutcracker” closer to death . . . well, then she might fall over, or miss her cue, or simply die a little inside from the grind of it.

Derek Dunn, a dancer with the Boston Ballet, applies rosin to his feet and ballet slippers backstage during a “Nutcracker” intermission at the Boston Opera House. (Josh Reynolds for The Washington Post)

For many families, “The Nutcracker” is a beloved holiday ritual, a respite from the season’s stresses, an oasis of beauty, innocence and poetry.

For the dancers, it is a marathon of pain, physical and existential. It is a minefield of injuries, illnesses and choking hazards. It can be crushingly boring.

It also involves incontinent children.

One year, corps de ballet member Harrison Monaco was onstage with the rest of the cast in the Pennsylvania Ballet’s “Nutcracker.” It was the top of the second act, when the Sugar Plum Fairy is greeting young Marie (in other versions, she’s named Clara), the child whose Christmas Eve dream brings her toys to life and deposits her into the Land of Sweets. In his peripheral vision, Monaco saw a mop poking out from the wings.

A member of the backstage crew was frantically trying to swipe it around the stage between the rows of performers, out of sight of the audience, because one of the little angel dancers in her tiny halo and wings had left a pool of pee behind her.

A few musical beats later, Monaco was leaping across the stage, dancing the Spanish variation, and — wouldn’t you know? — the half-swabbed puddle was right where he needed to land.

“I did my thing, and then I had to kneel and I was thinking, ‘Oh, this is wet. Oh no!’ ” he says. “But I had to be on my mark.” Exiting, finally, with wet knees, he found his colleagues in the wings in fits of laughter.

Performing with children raises other issues. The norovirus, for instance.

Now, no one’s saying that “Nutcracker” kids aren’t adorable, nor that they shouldn’t be part of this ballet, which is, after all, centered on a child. Also, kids in the cast guarantee parents in the seats; i.e., ticket sales. Dancers are well aware of the economics of “The Nutcracker,” that its long run of shows — a month or more — and that its family appeal can help fund a ballet company’s more artistically interesting but financially riskier productions for the rest of the year. Appearing in the first-act party scene, or swooping around as an angel or one of the little tykes popping out from Mother Ginger’s skirt is also good performing experience for young dance students. So kids in the cast — by all means, yes. But there can be a cost, as the Boston Ballet discovered last year.

Seo Hye Han massages her feet backstage. (Josh Reynolds for The Washington Post)

Dancer Lawrence Rines recalls that one of the littlest dancers was sick with norovirus, but he didn’t know it (yet), and he wanted to perform anyway. He threw up in one of the dressing rooms.

“Then, like wildfire, it spread, and by end, like, over 200 people had it, including kids, their parents, dancers, artistic staff,” Rines says. “There was a bit of hysteria.”

A cleaning team came in. Dancers were ordered to stay home if they had symptoms.

“I did hear of a kid in the wings taking the hat off the costume and throwing up in the hat,” Rines says. But no shows were canceled. They went on, of course, as they must.

For the professional dancers, the biggest “Nutcracker” woes involve their costumes, props and choreography. In the snow scene, for instance, little Clara encounters ballerinas dressed as snowflakes, whirling through a storm of silvery flurries, whipped along by some of the most gorgeous, dramatic music in the Tchaikovsky score. It is a guaranteed crowd-pleaser.

Yet, for the women onstage, the snow scene can be a stone-cold killer.

They’re circling around, jumping and spinning, desperate for air, but if they gasp, they’ll gag on fake flakes.

“Only closed-teeth smiles,” counsels dancer Elizabeth Walker of Los Angeles Ballet. “Breathe through your teeth.”

Sage Humphries massages her legs during intermission. (Josh Reynolds for The Washington Post)

Johnson remembers her first year as a snowflake, wearing an icicle crown that she hadn’t pinned down tightly enough. During a series of turns, it flew off, and she danced the rest of the scene alongside her snowflake sisters as the single, conspicuously bareheaded flake — a mortifying rookie mistake.

But another novice snowflake had it worse. At one point, standing at the far end of the line, this young and very green apprentice gracefully bent down over her front foot and then rose to do a little jump along with the other ballerinas. Except she was stuck in the mesh fabric of the wing.

“The wing, like, ate her crown,” Johnson says. “She had to go offstage and get unstuck. It was, ‘Oh, we just lost a snowflake.’ ”

Male dancers have their troubles, too. For Michael Sean Breeden, who recently retired from Miami City Ballet, his nightmare variation was the intensely athletic Candy Cane, performed to the fast, high-spirited “Trepak” music in George Balanchine’s version of “The Nutcracker.” The leading dancer carries a big hoop, and while he’s bouncing and leaping, he swings it overhead, flips it under his feet and whips it around himself like a jump-rope.

“There are 500 things that could go wrong,” Breeden says, and he’s suffered them all, including the smacked chin, banged skull, smashed toes and trips.

“I had a year where I’d get caught in the hoop in a different moment each time. Okay, so next time, I’d have my mental strategy, like, don’t pull your chin in. And I’d clear that hurdle, and the next sequence I hadn’t over-analyzed would get me.”

But even worse was his year with Boston Ballet, as the Bear in the first-act party scene, which he calls “possibly the worst thing I’ve ever done in my life.” He wore a big, furry head that complicated basic needs such as seeing and breathing. The choreography was virtuosic — difficult, strenuous turns.

“I was in tears,” he says, “before and after.”

And yet, the men and women interviewed for this article agreed that the men’s burden in most any version of “The Nutcracker” is nothing compared with what the ballerinas go through.

“When the boys are complaining, we’re like, ‘dude, you cannot be saying that. Whoa whoa whoa. Don’t be talking to us right now,’” Johnson says. “I’m sure they get hot, and their hearts beat quite a bit, but the girls are getting corns and are in pointe shoes every day.”

Often dancing two shows a day, feet squeezed into their pointe shoes from morning class through rehearsals and performances into the night, the women can develop sores between the toes where the bones rub together. These corns unleash sharp, shooting pain that makes every step excruciating.

“I’ve had broken bones, but a corn is this horrible nerve pain,” Walker says. The solution involves podiatrists and goop-scraping and antibiotics. Some try to numb their toes with Oragel. Or they cut holes in the pointe shoes. Walker knows some dancers who have had surgery to shave their toe bones.

“Nutcracker”-related injuries can affect a dancer for months afterward. Last year, the Washington Ballet’s Nicole Graniero developed tendinitis in one foot, which led her to overcompensate and injure her other foot. She’d dance in high heels in the party scene, changing into pointe shoes for the Snow Queen or Dew Drop or Sugar Plum or any of the nine roles in which she was cast. Throughout the run, she had two shows off. By her last performance, she could barely walk.

“Dancing ‘The Nutcracker’ gave me a six-month injury,” she says. This year, she’s happy to report, she’s been given a lighter load.

That end-of-the-series limp is familiar to every dancer who’s done “Nutcracker” time.

“The first week, you’re like, ‘I got this.’ But it’s a different story the fourth week into it,” Johnson says. “The fatigue. The repetition. You can get complacent.”

Yet, for dancers — as for all of us — the years spin faster and faster, and Christmas Eve, the ballet version that arrives around Thanksgiving, comes sooner and sooner.

Lawrence Rines, a dancer with the Boston Ballet, laces his shoes for his role as the lead Russian in “The Nutcracker.” (Josh Reynolds for The Washington Post)

One more season of “Nutcracker.” One season closer to the end of a career.

That’s when a philosophical approach helps. “The Nutcracker” is almost certainly the work that ballet dancers will perform the most in their professional lives. Dancers might be tempted to check out emotionally as fake snow plasters their lipstick or they struggle to keep smiling with a mustache coming unglued. But most try to find a challenge in the ballet, somewhere.

“If you’re going to do 46 shows in a row, you should get something out of it,” Rines says. “You shouldn’t just press ‘play.’ Our careers are so short, it’s kind of like wasting time — artistic time.”

Walker agrees. “In a dream world, I would love to do something fresh and new,” she says. But given the reality, she sets her mind on finding inspiration here and there, experimenting with a role, or simply enjoying her colleagues.

“The bonding experience, the crazy things that happen onstage, it’s a special time and a special tradition that we all share.”

“ ‘Nutcracker’ is what we have,” she says, “and it’s a pretty beautiful ballet, so it’s not as bad as it could be. It’s a fact of life.”