The blue lights are meant to discourage people from using drugs in store bathrooms by making it more difficult for them to see their veins. It’s an idea that’s been around for years but is getting a fresh look as a result of the nation’s opioid epidemic.

Colored bulbs casting an eerie blue glow in the restrooms of convenience stores, can very much disrupt the rituals of people who inject heroin and other drugs and who have been seeking the relative privacy of the stalls to shoot up.

“The hardest-core opiate user still wants to be accurate. They want to make sure the needle goes in the right spot,” said a University of Florida researcher and director of a retail industry-supported group that is looking at the lights’ effectiveness. The purpose of the blue light is to “disrupt that process” and force people to go somewhere else to take drugs, he said.

Many public health experts oppose the practice, saying blue lights make people more likely to hurt themselves and stigmatize those in the grips of addiction.

And, for people accustomed to injecting themselves, there are ways around the lights.