Be careful if you're squeezing a lime into a drink by the pool.

Lime juice, or juice from other drink adornments like lemons and celery, can mix with the sun to create painful blisters and burns.

Dermatologists say they often see patients in the spring and summer who have been mixing drinks outside. For example, some had lime juice on their palms after making margaritas, then sat in the sun without washing their hands.

"It is very painful because it's like a burn," said Dr. Larisa Geskin, associate professor of dermatology at the Columbia University Medical Center in New York. "Instead of burning yourself with the oil that splashes from your pan, it's basically a chemical reaction."

The condition, called phytophotodermatitis, is also called "margarita dermatitis," Geskin added.

A chemical in certain plants and fruits makes the skin more sensitive to sun, triggering a reaction when mixed with sunlight, said Dr. Vesna Petronic-Rosic, an associate professor of dermatology at the University of Chicago.

Those affected by it can get a painful rash and even second-degree burns with blisters.

"When you expose the skin to [the chemicals] and then you expose it to sunlight, you get an exaggerated sunburn reaction," Petronic-Rosic said.

The most common culprit? "Lime juice in margaritas," Petronic-Rosic said. But she's seen it with limes, oranges, celery, parsley and some carrots. "It's actually not uncommon at all," she said.

So what to do? Make sure to rinse off any juice while serving as bartender. "Basically you've got to really wash your hands well if you're making drinks by the pool," Petronic-Rosic said.

And it's not just your hands you have to worry about.

"If you're sitting by the pool drinking a margarita, you can get it around your mouth," Petronic-Rosic added. "Or you're taking tequila shots, you can get this on your lip. It's not at all fun."

Not everyone has the same sensitivity. Some might be affected; some not. In people who have darker skin tones, Petronic-Rosic said, this can create permanent dark spots.

Wear sunscreen, but know that even some sunblocks won't protect you because not all block UVA rays.

Rays also can reach through a window, Petronic-Rosic cautioned.

"You might get blisters," Petronic-Rosic said. "When you have blisters, you can get an infection. It's usually very uncomfortable."