Dreaming about celebrating Cinco de Mayo with a lime margarita by the pool? If you’re not careful, you might end up with more than just a hangover—you could develop a nasty rash. When life hands you limes, don’t squeeze them outdoors.

Be careful this Cinco de Mayo if you plan to enjoy a margarita. Second-degree burns and itchy rashes can develop if a stray splash of lime juice lands on your skin. The so-called “margarita rash” is a skin condition that can occur when a chemical compound found in limes interacts with sunlight. The rash could cause scarring, but that’s rare. The rash that develops is quite itchy at first and then it might get irritated and painful, potentially turn a dark red on your skin. Avoid this rash by carefully mixing drinks outside, and avoid handling citrus fruits before heading to the pool.

Dr. Andrew Newman of Phoenix-area Affiliated Dermatology shares more on this unusual condition.

“Margarita Rash, Margarita Burn, or Lime Disease, not to be confused with tick-related LYME disease, is a skin condition that occurs after the skin has been exposed to both lime juice and sunlight. Limes contain the chemical furanocoumarin, which sensitizes the skin to the damaging effects of the UV radiation in sunlight,” said Dr. Newman.

It’s not just lime juice that can cause the condition, known medically as phytophotodermatitis. Limes and lemons contain photosensitizing agents called psoralens, which can cause a sunburn-like reaction when they come in contact with skin. Other citrus fruits and celery also contain the compounds, furanocoumarins, that don’t mix well with sunlight. This chemical is found in limes and citrus fruits, along with celery, figs, fennel, and a number of other plants.

Newman goes on to say, “About 24-48 hours after exposure, an itchy, red, even blistering rash occurs in the area of skin in contact with the lime juice (with concomitant sunlight). This is referred to as phytophotodermatitis. Although long-term effects of margarita rash are uncommon, having the affected skin become darker (hyperpigmented) or even scarred is possible. An identical rash can be caused by skin contact and UV exposure with other plants, as well: various citrus fruits, figs, celery, parsnips, and carrots.”

Bartenders, food handlers, grocery workers, and those exposed to higher concentrations of psoralens with a longer period of UVA exposure could have a blistering reaction.

“Bartenders or anyone handling lime juice and absorbing sunshine may develop this condition. Bartenders commonly get this, also people who are picking limes off of a tree in their backyard, or those who are out on spring break and making cocktails for themselves for recreation,” Newman said.

How to Prevent Margarita Rash

To prevent margarita rash, wash your hands thoroughly after contact or avoid psoralen-containing foods and beverages while in the sun. You can avoid the rash by being careful when mixing those drinks and staying out of the sunlight after handling limes.

“The best way to protect yourself from this is to prevent it. Take caution in spilling the lime contents onto your skin, and any contents that do come in contact with your skin should be washed off with water. Avoiding or limiting UV exposure is also essential. Whenever you spill a margarita (or just lime juice) on your hand … and then that skin comes into contact with the sunlight you can develop this type of rash. The rash could cause scarring, but that’s rare. The rash that develops is quite itchy at first and then it might get irritated and painful, potentially turn a dark red on your skin,” he said.

If the rash has already developed, you may benefit from visiting your dermatologist to obtain a topical prescription anti-inflammatory medicine. Over-the-counter Benadryl can be used to alleviate itchiness and to help with sleep difficulties secondary to discomfort.

“If you’ve already developed a rash and you’re needing some relief, you just want to get a little cortisone cream over the counter,” Newman said. “Use it a couple of times a day and you’ll get some relief.”

So next time you are making your favorite summer drink remember to wash your hands immediately after—and as always, apply sunscreen with SPF 30 or higher when you are outside. If symptoms persist, contact a dermatologist.