Indigestion, stomach cramps and constipation are all signs of irritable bowel syndrome (IBS), a digestive condition estimated to affect one in 10 people worldwide.

There is no cure, although it can be managed with lifestyle and dietary changes. But discovering which foods trigger a bad reaction for individuals can be a long and painstaking process. It’s expensive too — a 2019 study of six European countries found that it cost healthcare systems between €937 ($1,087) and €2,108 ($2,445) per patient per year. That’s why Irish engineers Aonghus Shortt and Peter Harte founded FoodMarble, a startup that has invented portable devices, measuring just 5 centimeters squared, which test the hydrogen levels in a person’s breath — a key signal for digestive disorders.

“Humans shouldn’t be producing hydrogen on the breath,” explains Harte. It happens when food that couldn’t be digested in the small intestine moves to the large intestine where bacteria breaks it down, in a process called fermentation. That process releases gases, such as hydrogen or methane, that can cause pain or bloating. FoodMarble’s AIRE device, which launched in 2018, allows users to test for hydrogen after meals, giving them real-time feedback on what food is bad for their body. Readings are transmitted via Bluetooth to the FoodMarble app, where users can log what they eat, and over a course of weeks spot the ingredients that trigger symptoms.

Hydrogen breath tests have long been a method for diagnosing digestive conditions like lactose intolerance and more recently small intestinal bacterial overgrowth (SIBO), says Harte. But he adds that the technology has not been widely accessible or convenient — often requiring multiple trips to the hospital for testing. “By miniaturizing this, our aim is to democratize the technology,” he says. “We’ve got this huge cohort of patients who just haven’t had a way to overcome these difficult conditions. Our device is easy to use and understand, it gives them hope.” The global market for IBS treatments is also growing, expected to be worth more than $4 billion by 2028, up from $2 billion in 2020, according to a report by market research firm Research and Markets.