A recent consumer survey found that 68 percent of female pepper spray owners said they bought it for themselves. (PRNewsFoto/Mace Security International/PR NEWSWIRE)

Half a century ago, Daniel A. Gross writes on the Web site of Smithsonian magazine, a 29-year-old inventor named Alan Litman lived with his science-teacher wife, Doris, in Pittsburgh.

After one of Doris’s colleagues got mugged, the Litmans started talking about tools a woman walking city streets might use for self-defense, and soon they were experimenting with incapacitating chemicals that could be packed into an aerosol can.

They mixed kerosene, Freon and sulfuric acid to create their propellant. After trying “a dizzying array of chemicals that seared the eyes and face,” they settled on chloroacetophenone, a kind of tear gas, as their active ingredient. In 1964, Alan sent off patent applications for a spray can, nozzle and their chemical mixture. And they named their portable product after the terrifying spiked club wielded in medieval times: Chemical Mace.

In “The Forgotten History of Mace, Designed by a 29-Year-Old and Reinvented as a Police Weapon,” Gross notes that mace wasn’t innovative because of its chemical components, which had been around since World War II: “It was innovative because it repackaged a chemical weapon as a civilian product.”

He recounts the controversy that surrounded the mass production and sale of mace and its evolution from a weapon of self-defense to a tool of law enforcement. A sheriff in Illinois had himself maced on camera, to prove how “humane” it was. There were protests that if chemical weapons were outlawed in international warfare, we should not use them on fellow citizens.

As Gross writes, “In a society that embraces firearms while fighting gun violence, safety and self-defense can become puzzlingly relative concepts.”