Medical Mystery: What caused kids' summertime rashes?

A family that our practice treats emailed me one July about the very prominent rashes that appeared on the chests and abdomens of their sons, ages 4 and 7, during a vacation on the Mexican Riviera. Even after they returned home, the parents reported, the boys' rashes were getting more striking.

The parents attached pictures they had taken with their cell phones, and I could see that the children had very dark brown streaks down their chests and bellies. I asked them to come into the office for a workup.

When the children came in later that day, we obtained a more complete history. The family spent a week visiting the home of the boys' grandparents, and had enjoyed their days at the villa's attached pool.

At first, the parents had noted red streaks down the boys' fronts that stopped at the waistbands of their swim trunks. Over the week since they had returned home the streaks turned brown, and no amount of bathing washed off what looked like pigment.

The rashes were flat, the children had no pain or any other signs of illness, and otherwise their physicals were completely normal.

I thought about actinic dermatitis (skin changes from sun) but that is a disease of adults, not children. It did not look like sun poisoning or poison ivy. I was puzzled so I asked one of the other physicians who had spent much more time south of the border for a second opinion.

He looked, laughed, and asked the mother what they were drinking by the pool during the vacation. She said they had what her parents always served, fresh limeade.

The boys, my colleague informed me with a smile, had "the other lime disease." I was bewildered.

The children had what is called in adults "Mexican Beer Dermatitis."

Mexicans often serve beer or cocktails with a slice of lime and the lime juice can dribble down the chin and onto the chest, especially after a few drinks. If the skin is exposed immediately to the very bright sun of the summer in a tropical climate, a bright-red rash appears that turns dark brown in a few days. This pigmented rash can take as long as four months to completely fade away.

Adults enjoying a cocktail with just a slice of lime will get only a little bit of juice on their skin.

In boisterous young boys, playing by the pool all day drinking copious amounts of limeade, the amount of lime juice on the skin and exposed to the summer sun is tremendously more.

My patients' rashes covered half their chests and some of their bellies but not their backs or limbs, presumably because they didn't spill the juice there, or weren't so exposed to the sun's rays.

The diagnostic trick was the old saw, "looks bad, feels good," which is a fairly rare phenomenon. My colleague, Charles Pohl (now dean of students at Sidney Kimmel Medical College), said we could not call it Mexican Beer Dermatitis, given the boys' tender ages. But, he said, we could call it the "Other Lime Disease."

Gary A. Emmett, M.D., is professor of pediatrics at Thomas Jefferson University, and a frequent contributor to the "Healthy Kids" blog at philly.com/healthykids.

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