TAKE A SWIG. Go ahead. All at once, a flood of hot, spicy, sweet flavors converge in your mouth to create a warm, hell, yeah! sensation all the way down to your belly.

You've just experienced Fire Cider, an apple-cider-vinegar-based health tonic produced in the Berkshires by Shire City Herbals. Fire Cider is selling like gangbusters coast to coast - and locally at places like Weavers Way in Chestnut Hill, Essene Market and Art in the Age downtown and MOM's Organic Market, in Bryn Mawr.

Although Fire Cider officially launched in 2010 and is trademarked by Shire City Herbals, the recipe, and the notion of using vinegar as a health boost, is anything but new.

Vinegar - or vin aigre in French, meaning sour wine - was likely a mistaken revelation, the result of a cask of wine gone around the bend to reveal a new and pungent product.

Typically made with grapes, vinegar can be made from just about anything fermented, such as apples, dates, figs or rye. Referenced as early as 5000 BC, it was used by the Babylonians as a preservative and condiment.

Recommended as a health tonic by Hippocrates, vinegar also shows up in the Bible as a condiment.

In more modern times, vinegar was used to treat scurvy during the Civil War and to dress field wounds during World War I.

Apple-cider vinegar in particular has long been used as a folk remedy in New England, usually combined with honey and bold botanicals. And, although the FDA doesn't test or endorse health benefits to this or any other dietary supplement, the list of ailments that can purportedly benefit from a vinegar tonic is legion, from digestive woes and the common cold to dandruff and depression.

A growing fan base

Although such far-flung claims add an eye-of-newt quality to the remedy - which was likely sold by traveling medicine shows back in the day - the fact is that fans of the tonic love it.

"It blows my mind that there's so little science and research into the health benefits of vinegar. No one wants to put money into researching natural remedies," said Chris Mallam, a manager at Weavers Way in Chestnut Hill, which began carrying Fire Cider last November.

The tonic - spiked with organic raw honey, oranges, lemons, onions, ginger, horseradish, habanero pepper, garlic and turmeric - is the only infused vinegar that Weavers Way carries, and sales have already doubled. The 8-ounce bottle sells for $16, 16 ounces for $30, and Mallam is looking into growler portions.

Mallam started taking a shot of Fire Cider in the morning before he goes running. "It seems to reduce the lactic acid buildup in my muscles and I don't get as sore," he said. "And on cold mornings, it really warms me up inside. I like the way it tastes. It gives me a positive mood feeling. The stuff just makes me feel good."

An old-fashioned tonic

Amy Huebner had the same reaction when her then-fiance, now husband, Dana St. Pierre, gave her a gulp of his homemade tonic more than five years ago. "Dana had been making some version of Fire Cider since he was 19," she said. "And now he's 36."

The couple married in 2009 and moved to Dana's hometown of Pittsfield, Mass. "I'd been getting sick all the time with colds and flu when I lived in New York City," recalled Huebner, a board-certified holistic-health coach and a graduate of the Institute for Integrative Nutrition. "Dana said, 'Try this, it works for me.' And it really helped. Last year I was sick three days - that's a huge change for me."

The couple didn't have a big plan for how they were going to make a living in Pittsfield, so when a friend asked them to sell their Fire Cider at a Christmas market, they figured, why not. When it was met with enthusiasm, they decided to try selling on a larger scale. Amy's brother, Brian Huebner, also helps run the company.

Now produced in a solar-powered, shared commercial kitchen, Fire Cider is carried in more than 600 stores nationwide and online. In a typical week, Huebner and her team may siphon as much as 650 gallons of tonic into their distinctive amber bottles - made from recycled materials, natch.

Huebner is a big supporter of people making old-fashioned folk remedies like Fire Tonic at home. "It's very empowering to make your own medicine from ingredients that are literally growing in your back yard," she said. "I tell people how to make it all the time. But there are plenty of times when you're sick and you need something today. Fire Tonic takes four to six weeks to steep. That's our customer."

Their larger vision

Although there's been some backlash from the herbal community since Shire City Herbals trademarked the name Fire Cider, most of it playing out in social media, Huebner and her partners share a larger vision.

"Go to your co-op and look for something in a package that isn't trademark or copyrighted. You won't find it," she said. "That's just how business works. You have to play by the rules, and we can't do anything if we're standing on the other side of the moat. You have to get into the castle if you want to effect change."

One of the changes they are focused on is paying for local farmers to get their organic certification, an expensive and lengthy process. That enables a business to meet Shire's growing need for organic ingredients.

Whether you endorse natural remedies or not, Mallam suggests giving Fire Cider a try the next time you have a cold or need an energy spike. "It works for a lot of people," he said. "Maybe it will work for you, too."