People who often surf are more likely to become allergic to “natto” fermented soybeans than those who take to the waves less frequently, due to being stung by jellyfish, research by Yokomaha City University Hospital shows.

A research team headed by Naoko Inomata, associate professor of the hospital specializing in dermatology, examined 140 of its patients between November 2015 and December 2016 diagnosed with food allergies.

Among 13 patients in the group who had a natto allergy, 11 surfed. And many of the 11 tended to often go surfing.

In addition, among the 127 patients in the group who had food allergies but were not allergic to natto, only two patients had gone surfing.

“If surfers develop a food allergy, they would doubt natto as the cause," Inomata said.

A jellyfish creates an element in its body called polyglutamic acid (PGA), which produces bacillus subtilis natto. People who surf a lot are more likely to get stung by jellyfish, which makes it possible for them to develop the natto allergy more easily than others due to PGA being injected into their bodies, the study shows.

The characteristics of a natto allergy are symptoms of hives and difficulty breathing, which occur about half a day after eating the fermented soybeans. The symptoms tend to worsen, and it is difficult to determine the cause.