After infection the bacteria lives close to the surface lining of the stomach, underneath the layer of mucus, where it is protected from acid. As a result, acid secretion in response to a meal increases and it is thought that this excessive amount of acid damages the duodenum and leads to ulcer development. Duodenal ulcers are always benign but gastric ulcers can be benign or malignant and require careful investigation and follow up to ensure that they heal completely with treatment. These drugs, however, only play a small role in causing ulcers in the duodenum but may flare up existing ulcers. People at higher risk of complications include those over the age of sixty, those taking high doses and those with a past history of peptic ulcer or complications from these drugs.
Smoking also carries an increased risk of ulcers.
Complications of ulcers, including delayed healing, are more common in smokers than in non-smokers. Ulcers in this condition are often multiple, aggressive and resistant to therapy. This is discussed under health maintenance. At present there is no good evidence that widespread antibiotic therapy to eradicate HP in the population will prevent ulcer disease. This is the subject on ongoing debate by specialists and may change in the future.