I bet you didn’t know that the term “margarita photodermatitis” graced medical journals, but it does.

If you plan on enjoying a margarita this summer, handle the limes carefully. Limes, along with some other fruits and vegetables, contain chemicals called furocoumarins. Plants produce these chemicals as a defense mechanism against unwanted chomping. But when they come into contact with human skin, the furocoumarins act as photosensitizers, and make the tissue hypersensitive to ultraviolet light. It’s like reverse sunscreen.

When skin covered in limejuice is exposed to sunlight, the furocoumarins bond to the DNA in the skin’s outermost layer of cells, quickly causing serious tissue damage akin to spending hours sitting in sun. This pyphotodermatitis usually presents itself like terrible sunburn [slightly graphic], producing redness, swelling, and sometimes huge blisters [also slightly graphic].

Margarita photodermatitis “has been described most often as an occupational hazard among citrus workers and celery harvesters, because these foods contain high concentrations of furocoumarins,” says an article in the New England Journal of Medicine, but you can get it just as easily from shakily handling your summer drink. Though any blisters or burns you get will subside in a few days, the hyperpigmentation or skin darkening that follows can last for months or even years.

If you must have a margarita while sun bathing, make sure to wear extra sunscreen. Oh, and don’t let the limejuice outline some ridiculous pattern on your torso.

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Hat-tip to fellow science communicator Phil Torres, who fell asleep in the sun with a margarita and looked weird for a while.

Kyle Hill is the Chief Science Officer of the Nerdist enterprise. Follow the continued geekery on Twitter @Sci_Phile.