NSAIDs inhibit cyclooxygenase-1, or COX-1, an enzyme responsible for the biosynthesis of eicosanoids in the stomach, which increases the possibility of peptic ulcers forming. Also, NSAIDs, such as aspirin, reduce a substance that protects the stomach called prostaglandin. These drugs used in a short period are not typically dangerous. However, regular use can lead to gastritis. Additionally, severe physiologic stress ("stress ulcers") from sepsis, hypoxia, trauma, or surgery is also a common etiology for acute erosive gastritis. This form of gastritis can occur in more than 5% of hospitalized patients.Also, note that alcohol consumption does not cause chronic gastritis. It does, however, erode the mucosal lining of the stomach; low doses of alcohol stimulate hydrochloric acid secretion. High doses of alcohol do not stimulate secretion of acid. Chronic
Chronic gastritis refers to a wide range of problems of the gastric tissues. The immune system makes proteins and antibodies that fight infections in the body to maintain a homeostatic condition. In some disorders the body targets the stomach as if it were a foreign protein or pathogen; it makes antibodies against, severely damages, and may even destroy the stomach or its lining. In some cases bile, normally used to aid digestion in the small intestine, will enter through the pyloric valve of the stomach if it has been removed during surgery or does not work properly, also leading to gastritis. Gastritis may also be caused by other medical conditions, including HIV/AIDS, Crohns disease, certain connective tissue disorders, and liver or kidney failure.
People are usually advised to avoid foods that bother them.Gastritis is believed to affect about half of people worldwide. In 2013 there were approximately 90 million new cases of the condition. As people get older the disease becomes more common. It, along with a similar condition in the first part of the intestines known as duodenitis, resulted in 50,000 deaths in 2015. H. pylori was first discovered in 1981 by Barry Marshall and Robin Warren. Signs and symptoms
Many people with gastritis experience no symptoms at all. However, upper central abdominal pain is the most common symptom; the pain may be dull, vague, burning, aching, gnawing, sore, or sharp. Pain is usually located in the upper central portion of the abdomen, but it may occur anywhere from the upper left portion of the abdomen around to the back. Other signs and symptoms may include the following:

Nausea
Vomiting (may be clear, green or yellow, blood-streaked or completely bloody depending on the severity of the stomach inflammation)
Belching (does not usually relieve stomach pain if present)
Bloating
Early satiety
Loss of appetite
Unexplained weight loss

Causes
There are two categories of gastritis depending on the cause of the disease. There is erosive gastritis, for which the common causes are stress, alcohol, some drugs, such as aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), and Crohns disease. And, there is non-erosive gastritis, for which the most common cause is a Helicobacter pylori infection.