Diffuse gastritis is a condition that affects the lining of a person's stomach. There are many different things that are known to cause the condition. One of the common causes for diffuse gastritis is consuming large amounts of alcohol. Taking non-steroidal anti-inflammatory drugs, or NSAIDS, can also cause a person to suffer from gastritis. A person can also get the condition due suffering from things like burns, injuries, infections, and post major surgery. One of the most common types of symptoms with diffuse gastritis is upset stomach and pain. Vomiting and bloating may also be experienced with this condition.