Ventura, CALIF. — Go ahead and talk about the scraggly caterpillar sprouting on Gary Stewart’s upper lip. Tease him. Giggle at him.

It’s why the 47-year-old winemaker is growing his first-ever mustache.

“It’s ugly,” he said less than a week after he stopped shaving. “What I’m hoping is people are going to make fun of me and poke fun at me. And then I can tell them, ‘I’m growing this mustache so you’ll ask me what I am doing.’ ”

What he’s doing is joining the spirit of Movember, an international movement that uses just-sprouted mustaches — what Australians call a “mo” — as a way to talk about prostate cancer, testicular cancer and other men’s health issues.

Stewart, owner of Four Brix Winery in Ventura, Calif., is spurred by his father’s battle against prostate cancer and his own scare that led to 10 days of limbo as he waited for test results that turned out to be clear.

John Laurenzi, in his third year as a full-fledged Movember participant, is motivated by his father-in-law, Jerry Roberts. He died of prostate cancer a year ago at age 72.

In honor of Roberts and to get other men to deal with their own health risks, Laurenzi shaved his mustache and goatee. And then he started growing them again.

Last week, whiskered men gathered at a barbershop in Thousand Oaks, Calif., to do the same thing — shave themselves clean so they can dedicate November to repopulating their upper lips.

If the logic seems puzzling, that’s OK with Laurenzi. He’s looking for the same kind of reaction he gets when he tells people he’s a “Mo Bro.”

“They kind of just give you a little look ... like ‘huh?’ ” said Laurenzi, characterizing the transition from full growth to no growth to cultivating growth as a way to get, and then steer, people’s attention. “I need to create a change in order to incite discussion.”

Movember was born Down Under, where friends discovered they could use newly sprouted lip covers as a way to promote health awareness and ultimately raise money to fight and deal with prostate cancer and other illnesses. Last year, the worldwide campaign raised $126.3 million, about $15 million of which came from the United States.

“The mustache became our little hairy ribbon. You become a walking, talking billboard,” said Tom Whiteside of the U.S. Movember campaign. “The overarching goal is just to get men to talk about their health.”

So far this year, about 155,000 people have joined the U.S. campaign. Most are men but some are “Mo Sistas.”

The campaign was born out of the premise that mustaches, especially partially grown mustaches, are about as hip as pet rocks. But now mustaches are in, at least in the form of a fashion fad that ranges from refrigerator magnets and necklaces to coin purses and socks.

Whiteside isn’t sure the hipness helps.

“It needs to be a little uncool to make sure it sparks that conversation,” he said.