The blood in Herschell Gordon Lewis’ splatter films was made of Kaopectate.

The diarrhea medicine had the right consistency, though he had to tweak it to get a realistic shade of red.

An ad man, marketing wizard and part-time filmmaker whose prodigious use of blood put the “B” in B-movies, Mr. Lewis drew admiration from directors like James Gunn, creator of 2014’s “Guardians of the Galaxy.”

“He changed cinema,” Gunn tweeted after Mr. Lewis’ death Monday, at age 90, at his home in Pompano Beach, Florida.

screen-shot-2016-09-28-at-5-08-17-pmThe Godfather of Gore — who lived in the Chicago area for about 35 years — made about 40 cult films in the 1960s and 1970s, including “The Wizard of Gore,” “Blood Feast,” “Monster a Go-Go,” “Goldilocks and the Three Bares,” “2,000 Maniacs!” and “She-Devils on Wheels.”

Lovers of drive-in movies say his work influenced John Waters, Sam Raimi and Quentin Tarantino. Two rock bands adapted their names from his grindhouse classics: 10,000 Maniacs and the Gore Gore Girls. Waters did a cameo in Mr. Lewis’ 2002 movie “Blood Feast 2: All U Can Eat.”

And Mr. Lewis got a shoutout in 2007’s “Juno,” in which a pregnant, unwed teenager bonds with a prospective adoptive father as he praises the filmmaker as the “completely demented” creator of movies with “buckets of goo.”

Mr. Lewis was bemused by the attention, according to his son, Bob, viewing his films with a canny eye: He saw them as a way to make money.

Once, during an interview with a Chicago radio station, the host asked what kind of people watched his movies. His son remembers the answer went something like this: “We don’t really know — nobody’s figured out how to survey IQs that low.”

Bob Lewis says his father once observed: “We didn’t so much release movies as we excreted them.”

There was little Grand Guignol in his Depression upbringing in Pittsburgh. His father died when he was young, and his mother worked hard to keep him and his brother, Melvin, in clothes and food. He received bachelor’s and master’s degrees from Northwestern University, his son said.

Mr. Lewis worked for Chicago’s Morlock Advertising Agency. He did ads for Chicken Unlimited and the Bank of Highland Park, he said in a 1988 interview with the Chicago Sun-Times. He and his first wife, the former Barbara Rosenbaum, raised sons Bob and Michael in Highland Park.

He and a business partner, David Friedman, thought they could make money by shooting movies that Hollywood didn’t. Mr. Lewis’ initial film forays were built around curvaceous cuties. But after director Roger Vadim created the 1968 Jane Fonda romp “Barbarella,” he focused on gore.

Typically, he made one movie a year, shooting on a four-week schedule in Florida during the winter.

“We would simply drive a Volkswagen van to the location,” he told the Sun-Times. “We were in-and-out masters of location shooting. We had very little reverence for established techniques of filmmaking.”

He was particularly proud of his first movie, 1963’s “Blood Feast.”

“Prior to ‘Blood Feast,’ people died with their eyes peacefully closed — even in gangster movies,” he said. “There was a tiny circle of blood on a shirt front — not gallons of stage blood that we used. It changed forever the course of how people died onscreen.”

He lamented the unfinished dismemberment in his 1970 picture about a deranged magician, “The Wizard of Gore,” telling the Sun-Times, “The person who was supposed to handle the gore didn’t show up with the goat carcass.”

His 1975 film, “The Gore-Gore Girls,” was shot in a Wrigley Building conference room.

Mr. Lewis directed and did writing, production and cinematography, often working under the pseudonym “Seymour Sheldon.”

“He figured in Hollywood, everyone was named Seymour or Sheldon,” his son said.

Mr. Lewis also taught advertising at Roosevelt University, his son said, and for a time was an English instructor at Mississippi State University. At different points in his career, he did radio gigs in Racine, Wisconsin, and Oklahoma, his son said.

He hated winters, so he moved to Florida in 1979.

He had a successful marketing career with Communicomp and Lewis Enterprises. He wrote many books and articles about boosting profits with sales, advertising, strong copywriting and direct marketing — junk mail. He was a member of the Direct Marketing Association’s Hall of Fame.

An excellent tennis player and scuba diver, he enjoyed travel to Africa, India, and Madagascar.

Mr. Lewis’s son Michael died before him. He is also survived by his third wife, Margo; her children, Carol Nelson, Peggy Nelson, Paula Nelson, Sandy Nelson and John Easton; and two grandchildren. A private celebration of his life has been held.