Stomach aches have dozens of possible causes, ranging from something as simple as swallowed air or a skipped meal to conditions that need medical attention like appendicitis or gallbladder disease. Most of the time, the culprit is one of a handful of common triggers: gas, constipation, food reactions, stress, or a stomach virus. Where you feel the pain, how it started, and what else is happening in your body all point toward different explanations.
Why Location Matters
Your abdomen is divided into four quadrants, and different organs sit in each one. Pain in the upper right side involves the liver, gallbladder, and part of the pancreas. Upper left pain is closer to the stomach and spleen. Lower right pain is where the appendix lives, and lower left pain often involves the lower part of the colon. Pain that’s spread across your whole belly, without a clear center, usually points to something more general like gas, a stomach virus, or constipation.
This isn’t a perfect system. Pain can radiate, and your brain sometimes has trouble pinpointing exactly where internal organs are hurting. But if you can point to the spot that hurts most, it narrows things down considerably.
The Most Common Everyday Causes
Gas and bloating top the list. When bacteria in your gut break down certain carbohydrates, they produce gas through fermentation. Some people are more sensitive to this process than others. The foods most likely to trigger it fall into a group called FODMAPs, which includes onions, garlic, beans, lentils, wheat products, dairy (specifically the lactose in it), fruits high in fructose, and sugar alcohols used as artificial sweeteners. For sensitive individuals, the byproducts of fermentation cause cramping, bloating, and distension.
Constipation is another frequent offender. When stool backs up in the colon, it stretches the walls and creates a deep, achy pressure that can be hard to distinguish from other problems. Indigestion and acid reflux round out the usual suspects. Acid reflux alone affects over 825 million people worldwide, and the burning or gnawing pain it produces in the upper abdomen is often mistaken for a stomach ache rather than an esophageal problem.
Stomach viruses, commonly called stomach flu, cause generalized pain along with nausea, vomiting, or diarrhea. Food poisoning produces similar symptoms but tends to hit faster, often within hours of eating contaminated food.
How Stress Creates Real Pain
Your digestive system has its own nervous system, sometimes called the “second brain,” with nerve endings in every layer of your digestive organs. These nerves respond to everything: the food passing through, bacteria and their byproducts, stretching, inflammation, and chemical stress signals. They send pain information to the part of your brain that registers pain, which then activates the regions that process the emotional side of that pain.
This pathway works in both directions. Stress and emotions can amplify the perception of physical irritation in your gut, and gut pain can increase your stress response. Your brain reacts to both with stress hormones, which make symptoms worse. This is why anxiety and depression genuinely cause stomach aches in children and adults alike. It’s not imaginary pain. It’s a feedback loop between your brain and your gut that produces real, measurable symptoms.
Infections and Ulcers
A bacterium called H. pylori infects the stomach lining and is a major cause of stomach ulcers. The pain typically presents as a burning or gnawing sensation in the upper abdomen that may improve or worsen with eating. Testing is straightforward: a breath test, stool test, or blood test can identify the infection, and a course of antibiotics combined with acid-reducing medication clears it in most cases.
Stomach viruses and bacterial infections from contaminated food are shorter-lived but can produce intense cramping. If vomiting and diarrhea accompany the pain and resolve within a few days, an infection is the likely explanation.
Functional Gut Disorders
When stomach aches keep returning without a clear structural cause, a condition called visceral hypersensitivity may be at play. This means the nerve endings in your gut are dialed up, reacting more strongly to normal sensations like stretching, gas, or digestion. Physical pain and emotional stress constantly reinforce each other in this state.
Irritable bowel syndrome is the most common diagnosis in this category. It’s defined as recurring abdominal pain at least one day per week for three months, linked to changes in how often you have bowel movements or what they look like. Symptoms must have started at least six months before diagnosis. IBS doesn’t damage the gut, but it produces real, disruptive pain that responds to dietary changes (like reducing FODMAPs), stress management, and sometimes medication.
Stomach Aches in Children
Kids get stomach aches from many of the same causes as adults, but a few triggers are more common in childhood. Constipation, swallowed air, food intolerances, and anxiety are the most frequent non-serious explanations. Younger children may also develop abdominal migraines, which cause recurring episodes of belly pain without headache. Colic in infants is essentially unexplained abdominal distress that resolves on its own.
Generalized pain spread across more than half the belly in a child usually signals a stomach virus, gas, indigestion, or constipation. Cramping followed by diarrhea is typically gas-related and not serious. Pain that stays in one spot and gets progressively worse is a different story.
Warning Signs That Need Urgent Attention
Most stomach aches resolve on their own, but certain patterns signal something that needs emergency care.
Appendicitis often starts as a vague, nagging pain near the belly button with loss of appetite. Over the course of 12 to 24 hours, the pain migrates to the lower right abdomen and becomes progressively severe. It worsens with movement, coughing, or sneezing. Nausea, vomiting, and fever often follow.
Kidney stones cause an abrupt, sharp cramp in the lower abdomen that hits maximum intensity almost immediately, similar to a sudden runner’s cramp. Acute pancreatitis starts with mild upper abdominal pain that worsens after eating, then becomes severe and constant, sometimes with nausea, fever, and a rapid pulse. A bowel obstruction is especially likely if you’ve had previous abdominal surgery and develop bloating, severe pain, and an inability to pass gas or have a bowel movement.
The questions worth asking yourself: Is the pain severe enough to stop you from functioning normally? Are you vomiting and unable to keep liquids down? Is the pain different from anything you’ve experienced before, or is it a familiar pain that’s suddenly worse? If the answer to any of these is yes, that’s a reason to seek care promptly.