Most stomach ulcers aren't caused by stress — they're an infection you can cure

For most of the 20th century, doctors blamed peptic ulcers on stress, spicy food, and stomach acid — and treated them with bland diets and antacids that only eased symptoms while the sore kept coming back. Then in the 1980s, Australian researchers Barry Marshall and Robin Warren found a spiral-shaped bacterium, Helicobacter pylori, living in the stomach lining of ulcer patients. To prove it caused disease, Marshall drank a flask of the bacteria, gave himself gastritis, and cured it with antibiotics. The pair won the 2005 Nobel Prize in Medicine.

We now know H. pylori is behind the majority of peptic ulcers (the rest are mostly from NSAID painkillers like ibuprofen and aspirin). The bacterium burrows under the protective mucus of the stomach and neutralizes acid around itself, quietly inflaming the lining for years. It's remarkably common — carried by roughly half the world's population — though most people never develop symptoms.

Because it's an infection, it's curable: a short course of antibiotics plus an acid-reducing drug clears the bacteria and lets the ulcer heal for good. Prevention leans on the basics of avoiding fecal-oral spread — clean water, good hand hygiene, and safe food handling — since the bug is thought to pass between people via contaminated food, water, and close contact.