• Stomach ulcers occur when the layer protecting the stomach lining from stomach acid breaks down. This allows the stomach lining to become damaged.

This is usually caused by:

• An infection with Helicobacter pylori (H. pylori) bacteria.

H. pylori bacteria live in the stomach lining. The bacteria can irritate the stomach lining and make it more vulnerable to damage from stomach acid.

Infections are common. It's possible to be infected without realising it because the infection doesn't usually cause symptoms.

People of all ages can be infected. It's not clear exactly why some people are more vulnerable to the effects of H. pylori bacteria than others.

• Taking non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or aspirin – particularly if they're taken for a long time or at high doses.

NSAIDs are medicines widely used to treat pain, a high temperature (fever) and inflammation (swelling).

Commonly used NSAIDs include:

>ibuprofen

>aspirin

>naproxen

>diclofenac

Many people take NSAIDs without having any side effects. But there's always a risk the medication could cause problems, such as stomach ulcers, particularly if taken for a long time or at high doses.

• Lifestyle factors

There's little evidence that stomach ulcers are caused by:

>Spicy foods

>Stress

>Alcohol

But these can make the symptoms worse.

However, smoking can:

• increase your risk of developing stomach ulcers
• make treatment less effective