There are many different potential causes of stomach aches. In some cases, the condition that triggers the stomach ache is located in the stomach. However, a disorder in another area of the abdomen can also trigger stomach discomfort. Emotional factors can also cause stomach aches.

Some of the conditions that may cause stomach aches include:

• Appendicitis. An inflammation of the appendix (a small, finger-shaped pouch in the lower right abdomen) often causes pain that begins in the belly button and moves to the lower right abdomen. Loss of appetite, fever and vomiting are often associated with appendicitis.
  
  
• Constipation. Children may have this condition if their stools are small, dry and hard and it is painful to defecate. The stomach ache is likely to come and go and to feel like cramps. Changes in diet, such as increasing fiber and water intake, and use of gentle laxatives often cure or prevent constipation.
  
  
• Diarrhea. Characterized by frequent and runny, watery bowel movements that can be caused by a number of conditions, including influenza. Children with diarrhea often feel sick to their stomachs.
  
  
• Food-related problems. Overeating or eating certain types of foods (i.e., too spicy, sweet or greasy) can upset the stomach, a condition known as indigestion. In addition, food poisoning, food allergies and lactose intolerance (inability to digest the sugar lactose found in milk and other dairy products) may trigger stomach discomfort.
  
  
• Infection. Various infections can cause stomach aches. The most prominent is gastroenteritis, a condition usually caused by a virus that lasts between 24 and 48 hours. Symptoms include mild and intermittent stomach discomfort. In some cases, diarrhea and vomiting may also be present. Other infections that may cause stomach aches include urinary tract infections, strep throat, hepatitis, pneumonia, mononucleosis and ear infections.
  
  
• Injury to the abdomen. An abdominal injury can cause stomach ache. In some cases, this may be a sign of abdominal bleeding, a serious health threat. Children may suffer an abdominal injury from being punched or injured in sports, motor vehicle accidents or other mishaps.
  
  
• Medications. Use of some medications can upset the stomach. These include certain pain relievers (e.g., ibuprofen) and antibiotics (e.g., clindamycin).
  
  
• Stress. Emotional upset and anxiety are common sources of stomach aches. Children may be especially vulnerable when moving to a new community or experiencing turmoil at home or school. Depression is also a frequent source of chronic stomach aches (recurrent abdominal pain).
  
  
• Vomiting. Children may feel sick to their stomachs prior to, during and after vomiting. Motion sickness may irritate the stomach causing nausea and vomiting.
  
  
• Menstruation. Menstruating girls may experience abdominal cramps days before and during their monthly period.
  
  
• Irritable bowel syndrome (IBS). IBS causes chronic (long-term) or recurring abdominal pain. Both children and adolescents may have IBS, and some adults with IBS can recall IBS symptoms that were experienced during childhood.

Less common causes of stomach aches include giardiasis (infestation of the intestinal tract with a micro-organism), hernias (protrusion of an organ through a muscular wall), sickle cell anemia (inherited disorder of the red blood cells), pancreatitis (inflammation of the pancreas), peptic ulcers (open sore inside the stomach), inflammatory bowel disease (chronic inflammation of the intestines) and intussusception (telescoping of part of the intestine into another part).