"1) what causes stomach ulcers" -- The majority are due to H. pylori (Helicobacter pylori) infections and there may be other factors, such as frequent use of NSAIDs, osteoporosis medications and excessive acid production. Smoking can increase the risk for a peptic ulcer. They're not caused by "stress", spicy food or alcohol as was once believed, but excessive alcohol irritates the GI tract and alcohol use with an existing ulcer can make it worse. Uncontrolled stress can contribute to excessive acid production.
There are three kinds of ulcer -- (a) An esophageal ulcer, in the esophagus; (b) a gastric ulcer, in the stomach, (c) and a duodenal ulcer, in the duodenum, the first portion of the small intestine, which is what the stomach empties into. All can be referred to as peptic ulcers. Helicobacter pylori is pronounced HELL-lih-co-BACK-ter pie-LORE-ee.
H. pylori causes an inflammation of the stomach lining called gastritis. Medical terms that end in "itis" mean inflammation, although infection may also be present. The bacteria is found in most of us, about two-thirds of the world's population, and it's still not clear how it gets there in the first place and why some are affected but not others. It embeds itself into the mucus membrane of the esophagus, stomach or duodenum and is hard to get rid of. Treatment requires a multiple approach involving 2 antibiotics and an acid reducer or 1 antibiotic, a bismuth medication like Pepto-Bismol and an acid reducer. Strange as it may seem, H. pylori is susceptible to the bismuth in ordinary, OTC stomach meds. If the first treatment isn't aggressive enough or fails due to other reasons, there are 4 rescue regimens that can be repeated until the infection is successfully treated.
"2) what can you do to treat them...do they go away" -- I ended up explaining this in #1. And, no, peptic ulcers don't just away. If the cause of the ulcer isn't treated, why would the peptic ulcer go away? Right?
" 3) are they dangerous" -- They have the potential to be dangerous, especially depending on where they are. Peptic ulcers in any location can become bleeding ulcers and chronic blood loss as its own set of problems that result. Peptic ulcers in the stomach and duodenum can erode the wall of the structure all the way through, creating hole in the stomach or duodenum and allowing their highly contaminated contents to spill out into the sterile abdominal cavity. This is called a perforated ulcer and is a medical emergency as GI (gastrointestinal) contents DO NOT belong in the abdominal cavity. This leads to peritonitis, a massive infection in the abdomen. Another potentially dangerous situation is when adhesions (scars) form and if large enough or numerous enough may cause blockage in whichever structure they form.
"4) what are the symptoms" -- Although the basic symptoms for all three ulcers is the same, there necessarily is variation because of the locations. Common symptoms include a burning, gnawing pain that can be temporarily relieved by food (when the stomach is empty) (seen in duodenal ulcers) or a dull, aching pain that's sometimes aggravated by food (seen with gastric ulcers). Burning chest pain on swallowing is related to esophageal ulcers. With gastric ulcers, the pain tends to worsen at night and with all ulcers may stay for days or weeks, disappear for a while, but always comes back. Frequent belching, bloating. Upset stomach, a feeling of fullness. There may be nausea and "heartburn". More serious symptoms include vomiting blood (esophageal or gastric) or diarrhea that's dark red or sticky-looking black (duodenal). This indicates digested blood and most digestion takes place in the duodenum.