In a case of an oft-overlooked food preparation risk, a 40-year-old man showed up to an allergy clinic in Texas with a severe, burning rash on both his hands that had developed two days earlier. A couple of days later, it blistered. And a few weeks after that, the skin darkened and scaled. After several months, the skin on his hands finally returned to normal.

The culprit: lime juice and sunlight.

It turns out that just before developing the nasty skin eruption, the man had manually squeezed a dozen limes, then headed to an outdoor soccer game without applying sunscreen. His doctors diagnosed the man's rash as a classic case of phytophotodermatitis, according to a case report published Wednesday in the New England Journal of Medicine.

The condition is caused by toxic substances found in plants (phyto) that react with UV light (photo) to cause a burning, blistering, scaling, pigmented skin condition (dermatitis).

Specifically, the toxic chemicals are furocoumarins, which are found in some weeds and also a range of plants used in food. Those include celery, carrot, parsley, fennel, parsnip, lime, bitter orange, lemon, grapefruit, and sweet orange. Furocoumarins include chemicals with linear structures, psoralens, and angular structures, called angelicins, though not all of them are toxic.

Furocoumarins can enter skin cells, and for those that are phototoxic, become activated by exposure to ultraviolet light. The light causes the chemicals to form cross-linking bonds with the pyrimidine bases in DNA. This ties the double-stranded genetic material together, halting replication, which in turn leads to cell death and inflammation. //

Edgar Allan Esquire Ars Tribunus Militum
7y
2,830
Subscriptor
jtwrenn said:
I am just curious...did he squeeze a bunch of limes then not wash his hands? Is it as simple as wash places contacted by vegetables or this could happen to you? Or is this something we are just always rolling the dice on and there i no simple way to keep it from happening except to stay out of the sun?
Did a little googling out of curiosity:
(from webmd)
It takes between 30 to 120 minutes before psoralen is absorbed into your skin. If you can wash it off before it has time to absorb, you can prevent the chemical reaction to the sun.

Bartenders that work outdoors apparently call it "margarita burn" as a trade risk. //

Arstotzka Ars Scholae Palatinae
8y
863
Subscriptor++
Wash your hands and apply sunscreen! There are plenty of other reasons why sunscreen is a good idea above and beyond preventing this kind of horribleness.