Researchers at the University of North Carolina found that digging in the sand raises the risk of diarrhea by 27%. For kids under age 11, that number jumps to 44%.

Other studies have found high levels of E. coli bacteria in the top 8 inches of sand. In fact, levels can be almost 40 times those found in the water at the same beaches.

The contamination may come from storm sewer runoff, or from the feces left by birds or other animals. And once the germs are there, the sand provides a moist environment for the bacteria to rapidly reproduce.

To stay safe, use hand sanitizer after playing in the sand or water, until you can get to a bathroom to wash your hands with soap and fresh water.