Banana Boat is recalling its UltraMist spray-on sunscreens after five people in the past year have literally caught on fire from wearing it, the AP reports. It's not the sunscreen that's the problem—it's the bottle. Allow us to explain: Banana Boat, owned by Energizer Holdings (seller of batteries, razors, sunscreen, and lots of other stuff found near the registers at drugstores)  sold more than 20 million bottles that sprayed too much sunscreen out of the valve. The result: it didn't dry fast enough, making it more vulnerable to nearby flames. 

Poor Brett Sigworth of Massachusetts figured that out this past summer at his backyard barbecue. Right after he sprayed on Banana Boat's Sport continuous spray, he went to tend the grill, and his entire body immediately lit on fire. Photos from a video by WBZ-TV in Boston showed that the burns lined up with sunscreen sprays. (Warning: The photos are not pretty.) A couple days after the story blew up in late May, Banana Boat vowed to investigate the cause.

Again, sunscreen itself is usually not flammable. As Anahad O'Connor explained in The New York Times after the Sigworth case, when it's sprayed from a can it can become flammable. Turning something into an aerosol requires flammable ingredients like alcohol, which is why products like spray sunscreen and hairspray include flammability warning labels. Alcohol usually should evaporate quickly, but because Banana Boat spray valves let out too much, the alcohol did not evaporate quickly enough.

So get rid of your UltraMist Banana Boat bottles! Or, you know, maybe just don't smoke a cigarette after spraying it all over your exposed flesh.

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Serena Dai