The feeling of an internal heat or burning sensation without an external fever is a common and unsettling physical symptom. This subjective experience, often described as a fire beneath the skin, can originate from numerous systems within the body. Pinpointing the source requires investigating issues ranging from chemical irritations in the gut to changes in hormone levels or misfiring nerves. Understanding these origins is the first step toward finding relief.
Burning Sensation in the Digestive Tract
The most recognized cause of internal burning is related to the upper digestive system, specifically heartburn. This sensation arises when the lower esophageal sphincter, the muscle separating the esophagus from the stomach, weakens or relaxes. Highly acidic stomach contents then flow backward, or reflux, into the esophagus.
Since the esophageal lining lacks the protective mucus layer of the stomach, this chemical exposure causes a painful, burning feeling behind the breastbone. When this acid reflux occurs frequently, typically more than twice a week, it is diagnosed as Gastroesophageal Reflux Disease (GERD).
The digestive tract can also produce localized burning sensations lower in the abdomen due to peptic ulcers. These are open sores that develop on the inner lining of the stomach (gastric ulcers) or the upper part of the small intestine (duodenal ulcers). The corrosive digestive juices, including hydrochloric acid and pepsin, irritate the exposed tissue. This typically results in a gnawing or burning pain in the upper mid-abdomen.
The presence of the Helicobacter pylori (H. pylori) bacterium or the long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) are the primary reasons ulcers form. These factors compromise the stomach’s protective lining, creating vulnerabilities where acid causes damage. Managing these issues focuses on reducing acid production and allowing the irritated tissues to heal.
Systemic Causes: Hormonal and Metabolic Changes
A generalized feeling of internal heat can be traced to systemic changes that disrupt temperature regulation. Hormonal fluctuations, particularly the hot flashes associated with perimenopause and menopause, are a prime example. These waves of heat are caused by a narrowing of the thermoneutral zone in the hypothalamus, the brain’s internal thermostat.
The drop in estrogen levels destabilizes the hypothalamus, causing it to trigger an exaggerated heat-loss response. This response initiates rapid cooling mechanisms, such as peripheral vasodilation (widening of blood vessels) and profuse sweating, leading to the characteristic feeling of heat spreading through the chest, neck, and face.
Metabolism is another systemic driver of internal heat. Hyperthyroidism, an overactive thyroid gland, causes the entire metabolism to run at an accelerated pace. The excessive production of thyroid hormones generates surplus heat as a byproduct of heightened cellular activity. This metabolic overdrive results in chronic heat intolerance and a persistent feeling of being warm or flushed.
Neurological Explanations: Nerve Pain and Dysfunction
A burning sensation localized in the extremities can be a symptom of neuropathy, a nervous system problem. Neuropathy involves damage or dysfunction to the peripheral nerves. When compromised, these nerves spontaneously misfire signals, interpreting pain as a burning or electrical sensation.
Small fiber neuropathy (SFN) involves damage to the small nerve fibers in the skin responsible for sensing temperature and pain. This damage leads to a characteristic burning, tingling, or prickling sensation, most commonly starting in the feet and hands. While diabetes is a common cause, neuropathy can also result from autoimmune disorders, vitamin B12 deficiencies, or toxin exposure.
Complex Regional Pain Syndrome (CRPS) is another neurological cause, often developing after a limb injury. The prolonged burning pain associated with CRPS is disproportionate to the original injury and involves a malfunction in how the nervous systems process pain signals. CRPS can also include changes in skin temperature, color, and swelling.
The Role of Stress and Anxiety
Psychological distress can manifest as physical symptoms, including internal burning or flushing. This is a direct result of the body’s innate “fight or flight” response, governed by the sympathetic nervous system. When a person is anxious or stressed, the body releases a surge of catecholamines, such as adrenaline and cortisol.
These stress hormones redirect blood flow away from the core and toward major muscle groups, causing a sensation of flushing or warmth in the chest and limbs. The increased heart rate and muscle tension accompanying this response heighten physical awareness, leading to the perception of a sudden, internal heat wave. This burning sensation is a somatic symptom, a physical manifestation of a psychological state.
When to Seek Medical Consultation
While many causes of internal burning are manageable, certain accompanying symptoms warrant medical attention. Any sudden burning chest pain, particularly if it radiates to the jaw, arm, or back, could indicate a heart issue and requires immediate evaluation.
If the burning sensation is accompanied by other symptoms, consult a healthcare provider:
- Difficulty swallowing (dysphagia), which may suggest an esophageal obstruction or severe irritation.
- Unexplained or unintentional weight loss.
- Recurrent vomiting.
- Bloody or black stools, suggesting a serious gastrointestinal or systemic disease.
- New muscle weakness, numbness, or a persistent fever, requiring a workup for neurological or infectious causes.