A stray splash of lime juice can turn fun in the sun into a second-degree burn.
Summer means outdoor celebrations and, ideally, backyard margaritas. But a little-known agent in limes can cause a burning rash that takes months — even years — to heal.
Take Aaron Peers, a Floridian who made margaritas outdoors on a holiday weekend in 2015. Burns appeared on his hand the next night. A massive blister later formed. The culprit? Sunshine and lime juice. Or, more specifically, ultraviolet light and furocoumarin -- a chemical found in limes.
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The two cause a direct toxic reaction to the skin known as phytophotodermatitis, said Dr. Rosemary deShazo, an allergic skin disease specialist with University of Utah Health Care. It's also called "lime disease" or "margarita dermatitis."
Effects of the reaction begin within minutes, with a rash forming within 24 hours. Skin once covered in lime juice becomes red and sometimes blisters. The rash can burn and feel painful, taking on its worst appearance by 72 hours, deShazo said.
The fairer the skin, the nastier the reaction, she noted, and wet skin, excessive heat and sweating can make things worse, too. Blisters or an infected rash can lead to scarring.
Eventually, a blistering, red rash will crust over, leaving "a brownish discoloration of the skin," deShazo said. This discoloration slowly improves over months or even years.
"The classic scenario we talk about is a rash after squeezing limes for margaritas, but phytophotodermatitis is also seen in fruit and vegetable processing," deShazo said.
Reactions can occur while hiking or gardening, she added, even when wearing certain Hawaiian leis made from mokihana trees found in the state.
Other plants well-known to cause phytophotodermatitis include celery, fennel, cow parsnip and parsley as well as citrus fruits such as key lime, lemon and grapefruit, she noted.
The best treatment option for phytophotodermatitis is prevention, deShazo said. Sip that margarita while wearing a wide-brimmed hat. Cover legs and sleeves, if you can, or sit underneath an umbrella. An SPF-50 sunscreen with broad-spectrum UVA/UVB protection helps, too, she added.
And if you suspect some lime juice dripped onto your skin, simply clean the area with soap and water as soon as possible.