A burning sensation under the left rib is normally caused by organs that lie underneath, and might include spleen irritation, splenic fixture syndrome, costochondritis, a pinched nerve in the thoracic spine, a broken rib, pneumonia, pleuritis, pneumothorax, lung cancer, heart attack, spleen disorders like an enlarged spleen, angina pectoris, pancreatic cancer, pancreatitis, torn muscles, kidney diseases, chest or abdominal trauma, pericarditis, gastric ulcers, an aneurysm or herpes, as reported by HealthHype. The burning sensation or pain can also be attributed to psychological effects, like a neurotic heart; however, it is crucial that medical experts attempt to identify whether there are physical causes at fault first.
Some of the causes can be rather mild, and are considered to be temporary, as they will leave eventually. For example, spleen irritation could be a result of strenuous exercise; however, the burning sensation or pain will normally dissipate after getting some rest.
In other situations, the cause of spleen irritation is much more severe, and should be treated immediately. For example, costochronditis is caused by inflammation to the cartilage that connects the ribs and the breastbone, while splenic fixture syndrome is caused by gas that is trapped at the area between the colon and the spleen.