The Saturday Night Live star is Christian Siriano's ultimate saleswoman 
Credit: Sean Zanni/Patrick McMullan via Getty

A few years ago, Leslie Jones went on Twitter to lament that no one wanted to dress her for the premiere of Ghostbusters. Quickly, Christian Siriano — a designer who has built his reputation and career on dressing all body types — swooped in and offered to dress the Saturday Night Live star in her dream gown, a Pretty Woman-esque off-the-shoulder red stunner.

Turns out, it became a highly coveted look.

“We’ve sold hundreds of that red gown,” Siriano tells PEOPLE when he stopped by our New York offices recently to discuss his support of the campaign, a new initiative by dermatology drug company Dermira that encourages people to share their stories of excessive sweating and hyperhidrosis using the hashtag #checkmysweat.

“Certain celebrities, when they wear clothes, people immediately want it,” says Siriano. “Our wildcard is when we dress Leslie.”

Premiere Of Sony Pictures' "Ghostbusters" - Arrivals
Credit: Jeffrey Mayer/Getty

Perhaps it helps that every time the star, 51, wears one of his looks, she declares her love of the shape, fit, silhouette and color on social media. She’s as enthusiastic about her love of Siriano as she is about the Olympics or SNL co-star Colin Jost.

“She’s my hype woman,” says Siriano.

That goes for almost every time she’s worn clothes, including the blue jumpsuit to the Emmys in 2016, a blue suit for the Perfect Game 20th Anniversary bash and a white tuxedo mini to the Time 100 Gala in April.

From left: Leslie Jones in Christian Siriano at the 2016 Emmys, a Perfect Game 20th anniversary event, and the 2017 Emmys.

“I just feel amazing,” she cheered on Instagram of her 2017 Emmys look, a black embellished gown.

Most recently, she wore an iridescent suit to the Emmys in September. Jones boasted about her look on social media again. “Man I looked good giving @iamreginaking her Emmy!!” she wrote.

Behind the scenes, it was a stressful moment: He fit her in the look the night before his New York Fashion Week show, at a point when he was incredibly busy. But he did not hesitate to help her — and the look became an instant hit with women who asked to score the shimmery design for themselves.

“A lot of people wanted that suit!” says Siriano.

70th Emmy Awards - Arrivals
Credit: Kevin Mazur/Getty Images

While Jones is talented at hyping the designer, the clothes themselves are what really speak to people, he notes.

“I think people really resonate with seeing different people on the runway or different people on the red carpet that look more like them,” he says. “You have to put things in people’s face for them to get it sometimes.”

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“I hated when people said, ‘you only make clothes for this certain person.’ I’m like, well that’s just not true,” he continues. “So, you have to put it in their face, and what I’ve been trying to do, so that the customer understands that she can buy any size we have available.” (Siriano carries up to size 28.)

Another thing he’s putting in people’s face: Sweating.

He teamed up with Dermira to launch, a destination to help people to feel better about hyperhidrosis, or excessive sweating. On the site, he provides tips to deal with sweat when choosing looks and encourages people to share their own stories.

“This is a real medical condition, and a lot of people struggle with it,” he says. “I’ve dressed so many people, and it can be a really hard thing for people. They won’t wear something, they don’t want to go to an event. I want to say that it’s not this horrible thing that you can’t live your life on.”

Christian Siriano Celebrates The Launch Of New Store, The Curated NYC, Hosted By Alicia Silverstone
Siriano with Alicia Silverstone and Debra Messing.
| Credit: Jamie McCarthy/Getty

The secret, he says, is choosing styles and fabrics that are better suited to potential sweat breakouts, like a pretty print or cotton and linen.

“I remember dressing Angela Bassett and the sweating showed,” he says of Bassett’s yellow cape silk gown for the 2016 Emmy Awards. “I wish I would have known, because I could have guided her in a different direction.”

Ultimately, whether it’s tackling sweat challenges or flaunting your shape, his grand goal is to help women to feel fabulous.

“No matter who you are, you can still have fun with fashion,” he says. “It goes back to my whole idea of supporting all different types of people and trying to make themselves feel great about themselves. We just want to make people feel good.”