Sunscreen is supposed to safeguard against solar burn, but a handful of incidents are on record in which people seemed to literally burst into flames while wearing a spray-on product.

The U.S. Food and Drug Administration has on file five incidents—and Canadian regulators have noted another—in which people applied spray-on sunscreen and, after approaching a barbecue grill, lighting a cigarette or standing near a citronella candle, their skin caught fire, causing severe burns that needed medical treatment.

In each instance the user of the sunscreen apparently believed the spray was dry. There had been no “blowtorch effect” in which the flame erupted outward when the aerosol vapor was applied close to a fire source.

So what really happened?
As might be expected, what caused the burns remains contentious. Energizer Holdings, Inc., which makes the Banana Boat spray sunscreens involved in all these incidents, issued a recall last year because of the danger of burns. But the company claims that the spray does not normally pose any threat to a sunbather. Rather, a faulty spray valve on the can dispensed too much sunscreen so that the product took longer to dry than usual and was still moist when exposed to a flame. Chemicals typically used to make aerosols—propane, dimethyl ether, volatile hydrocarbons and alcohol are all flammable, but alcohol usually evaporates quickly, decreasing fire risk.

Energizer has redesigned the valve and “rigorously tested it through our comprehensive safety and quality assurance processes,” the company says. New products began shipping in November 2012.

Regulators, meanwhile, maintain that the problem could extend beyond Banana Boat sprays. Many sunscreen sprays contain flammable ingredients, so the agency last month issued a warning: “We recommend that after you have applied a sunscreen spray labeled as flammable, you consider avoiding being near an open flame, sparks or an ignition source," said Narayan Nair, a lead medical officer at the FDA. The agency cautions that even if skin feels dry, the wearer of any flammable sunscreen should avoid open flames or any material that can throw sparks.

None of this has changed advice about the dangers of unprotected exposure to the sun. You still have multiple options to avoid sunburn without barbecue burn: nonflammable sunscreen lotions, wearing long sleeves or taking extra care with sprays.