Looking to relieve her miniature dachshund Parky's arthritis, Teressa Sworsky of Plainfield, Ill., discovered hemp oil.

After researching the exploding industry of products infused with cannabidiol, or CBD, Sworsky, 36, a registered nurse and mother of two who works full time in the corporate office of a hospital system, soon learned about other uses for the substance, which is most often derived from hemp, a plant in the cannabis family, but without the mind-altering properties of THC. After giving the CBD oil to her dog, she decided to try it for herself as an alternative to her side effect-ridden anxiety medication.

It worked, said Sworsky, who realized she could also sell it for side cash.

CBD oil, whether in lotions, balms or inside of a dropper bottle like the kind Sworsky uses for herself and her pet, is the latest in a string of products that women, many of them mothers, are selling and recruiting others to sell — a modernized version of a decades-old trend. Whether Tupperware, makeup, jewelry or patterned leggings, selling products directly to customers, often friends and neighbors through at-home parties and social media, has become increasingly popular in recent years.

According to the Washington-based Direct Sellers Association's most recent data, 18.6 million people were involved in the direct selling of $34.9 billion in products in 2017, whether they did so part time, full time, or signed up with companies to receive a discount on their favorite products. Across the U.S., 73.5 percent of direct sellers were women, said Joseph Mariano, the association's president and chief executive.

Hemp is a new frontier. In the U.S., the availability of CBD products grew by more than 80 percent in 2018, to about $591 million, according to market research from Chicago-based Brightfield Group. CBD oil is touted as a way to ease migraines, sleeplessness and seizures, among myriad other afflictions. But research is still emerging, and CBD is not regulated by the Food and Drug Administration.

Experts say the increasing popularity of the direct-selling industry could be part of the overall rise of the gig economy in the social media age. And it's appealing to women because the flexibility of the job offers moms a way to earn money while also taking care of responsibilities at home.

"It's the idea that I can start working when I want to work and stop working when I want to," said Julie Hennessy, marketing professor at Northwestern University's Kellogg School of Management.

And social media only makes it easier, Hennessy added. "If you go back to the Avon lady of 50 years ago, she had to call all her friends … and set up appointments," she said. "But now you can set up a [Facebook] site … and you can instantly get to 1,000 people or 2,000 people or 10,000 people without feeling awkward about asking a friend to buy something."

To achieve success, many sellers of CBD oil products, like Sworsky, rely on multilevel marketing, where they recruit others to sell beneath them and collect a percentage of their sales. While there are stories of people who expand this kind of side job into a successful business that supports their families, experts say there are many more who only make a few extra dollars or lose money if they're required to purchase inventory upfront.