Why Can an Illness Affect Your Autonomic Nervous System?
The autonomic nervous system regulates many functions you do not consciously control
Illness can disrupt autonomic nerves, signaling, circulation, or regulatory pathways
Symptoms may involve the heart, digestion, sweating, temperature, cognition, and more
Your heart suddenly races when you stand. You become dizzy in the shower. Your hands and feet feel unusually cold. You sweat too much—or hardly at all. A meal leaves you nauseated or bloated. Exercise that once felt easy now produces overwhelming fatigue, palpitations, or brain fog.
These symptoms may seem unrelated. But one system helps regulate all of them: the autonomic nervous system.
This raises an important question: Why can an illness affect your autonomic nervous system?
The autonomic nervous system is an extensive regulatory network connecting the brain, spinal cord, peripheral nerves, heart, blood vessels, digestive tract, sweat glands, bladder, pupils, and other organs. An illness that interferes with this network can therefore produce symptoms in several seemingly unrelated parts of the body.
Autonomic dysfunction is not one disease and does not have one cause. Diabetes, neurologic disorders, autoimmune disease, medications, toxic exposures, infections, and other illnesses can affect autonomic function through different mechanisms.
What does the autonomic nervous system actually do?
The autonomic nervous system regulates body functions that ordinarily occur without conscious effort.
When you stand, for example, gravity causes blood to shift toward the lower body. Your autonomic nervous system rapidly helps adjust heart rate and blood-vessel tone so that enough blood continues reaching the brain.
When you become hot, autonomic pathways help control sweating and circulation near the skin. When you eat, autonomic nerves participate in digestive movement and secretion. The same broad system contributes to pupil responses, bladder function, sexual function, blood pressure regulation, and other automatic processes.
The autonomic nervous system is commonly divided into sympathetic and parasympathetic components, but normal autonomic function depends on coordinated regulation rather than simply having one side turned “on” and the other turned “off.”
Because autonomic control reaches so many organs, dysfunction can produce a surprisingly broad collection of symptoms.
Dysautonomia is not one specific diagnosis
The term dysautonomia broadly refers to abnormal functioning of the autonomic nervous system. It describes a problem with autonomic regulation rather than identifying a single underlying disease.
Some autonomic disorders primarily affect the nervous system itself. Others occur secondary to another medical condition.
Postural orthostatic tachycardia syndrome (POTS), neurogenic orthostatic hypotension, autonomic neuropathy, and other disorders can all involve autonomic dysfunction, but they are not interchangeable diagnoses.
Likewise, experiencing dizziness, tachycardia, sweating abnormalities, gastrointestinal symptoms, or heat intolerance does not by itself establish that someone has dysautonomia. These symptoms have many potential causes and need to be interpreted in the broader clinical context.
Illness can affect autonomic nerves directly
One mechanism is injury to the nerves responsible for autonomic function.
Autonomic nerve fibers travel throughout the body and carry signals between the central nervous system and organs such as the heart, blood vessels, gastrointestinal tract, bladder, and sweat glands.
Diabetes is a well-established example. Over time, diabetes can damage peripheral nerves, including autonomic nerves. Depending on the nerves involved, diabetic autonomic neuropathy may affect blood pressure, digestion, bladder function, sweating, sexual function, and other processes.
Other metabolic, toxic, inherited, neurologic, and systemic illnesses can also injure autonomic pathways.
Small nerve fibers can be involved
Some autonomic functions depend on small peripheral nerve fibers. These fibers can also carry sensory information related to pain and temperature.
When small fibers are affected, a patient may have a mixture of sensory and autonomic symptoms. Burning pain, abnormal temperature sensation, altered sweating, heart-rate changes, gastrointestinal problems, and orthostatic symptoms can sometimes occur together.
Importantly, conventional nerve-conduction studies and EMG primarily evaluate larger nerve fibers. A normal EMG therefore does not evaluate every type of peripheral nerve dysfunction.
This is one reason symptoms involving autonomic or small-fiber function may require a different diagnostic approach from symptoms caused by large-fiber neuropathy.
Immune and inflammatory processes may affect autonomic regulation
Not every autonomic disorder results from straightforward destruction of a nerve.
Autoimmune diseases can affect peripheral nerves or other components involved in autonomic signaling. In some autonomic disorders, antibodies directed against receptors or other neural targets have also been investigated.
Inflammation may influence autonomic regulation through several pathways involving the nervous system, immune system, blood vessels, and signaling molecules.
However, the mechanisms differ among diseases, and evidence of autonomic dysfunction does not by itself establish that an autoimmune or inflammatory process is responsible.
Infections can sometimes affect autonomic function
Autonomic dysfunction has been described with a variety of infectious diseases. The mechanisms are not necessarily the same for every infection.
In some circumstances, infection can directly affect neurologic structures. In others, toxins produced during infection can interfere with autonomic transmission. Immune responses triggered by an infection may also contribute to neurologic complications.
Autonomic symptoms may occur during an acute illness, but they can also appear or persist after the acute infection has passed.
This post-infectious pattern has received increased attention because of research into chronic symptoms following COVID-19 and other infections.
What are researchers learning from post-infectious illness?
Post-COVID illness has provided researchers with an opportunity to study autonomic abnormalities in a large population of patients who developed persistent symptoms after an infection.
Studies have described orthostatic intolerance, POTS, altered heart-rate variability, blood-pressure abnormalities, and other findings consistent with impaired autonomic regulation in subsets of patients following COVID-19.
A 2026 study published in Scientific Reports evaluated 39 patients with long COVID and 22 healthy controls using heart-rate variability and blood-pressure measurements during tilt-table testing. The long-COVID group demonstrated altered autonomic responses during upright tilt, including findings suggesting impaired adaptation to orthostatic stress.
The study does not mean that every person with persistent symptoms after COVID-19 has dysautonomia. It does, however, add to evidence that measurable autonomic abnormalities can occur after infection in some patients.
Researchers continue to investigate possible mechanisms, including immune dysregulation, inflammation, vascular abnormalities, altered autonomic signaling, and small-fiber involvement. It is possible that more than one mechanism contributes, and that the mechanism differs among patients.
Lyme disease and autonomic dysfunction
Lyme disease provides another important area of investigation.
Lyme disease can involve the nervous system, and autonomic symptoms have been described in patients with Lyme disease and in some patients with persistent symptoms following treatment.
A 2024 review by Adler and colleagues from Johns Hopkins examined whether dysautonomia might contribute to symptoms experienced by some patients following Lyme disease. The authors noted similarities between symptoms reported in post-treatment Lyme disease and other infection-associated chronic illnesses in which autonomic dysfunction has received greater research attention.
At the same time, the authors emphasized an important limitation: dysautonomia has not yet been established as a complication of Lyme disease in the medical literature, and research specifically examining this relationship remains limited.
This distinction matters. Dizziness, palpitations, exercise intolerance, gastrointestinal symptoms, temperature intolerance, or brain fog in someone with Lyme disease may warrant consideration of autonomic dysfunction, but those symptoms do not prove that Lyme disease is responsible. Other causes may need to be considered.
Why can autonomic dysfunction cause symptoms in several body systems?
The answer lies in what the autonomic nervous system controls.
A problem affecting one regulatory network can potentially influence several organs at once. This is one reason symptoms can affect several body systems at the same time without necessarily representing a separate disease in every organ.
Autonomic dysfunction can potentially affect:
- Heart rate: tachycardia, palpitations, or abnormal heart-rate responses
- Blood pressure and circulation: dizziness, lightheadedness, weakness, or fainting
- Digestion: nausea, bloating, altered motility, constipation, or diarrhea
- Sweating: excessive sweating or reduced sweating
- Temperature regulation: heat or cold intolerance
- Exercise tolerance: difficulty maintaining activity or recovering from exertion
- Bladder function: difficulty with storage or emptying
- Pupillary responses: problems adjusting to changes in light in some disorders
Patients may experience only one or two of these problems, while others develop a broader pattern. The particular symptoms depend on which autonomic pathways are affected and what underlying condition is responsible.
Why can standing make autonomic symptoms more obvious?
Standing is one of the body’s everyday autonomic stress tests.
When you move from lying down to standing, blood shifts downward. The body normally compensates within seconds by adjusting vascular tone, heart rate, and other cardiovascular responses.
If those compensatory mechanisms are impaired, symptoms may become particularly noticeable when standing. A person may experience lightheadedness, palpitations, weakness, blurred vision, fatigue, or difficulty thinking.
Some patients develop orthostatic hypotension. Others experience an excessive increase in heart rate consistent with POTS. Still others can have significant orthostatic symptoms without meeting the diagnostic criteria for either condition.
This is why heart rate, blood pressure, symptoms, medications, hydration, and the clinical history all matter when evaluating symptoms that occur upright.
Why can heat make autonomic symptoms worse?
Heat places another demand on autonomic regulation.
To release heat, blood vessels near the skin dilate and sweating increases. These responses can reduce the amount of blood immediately available to the central circulation, particularly when a person is also dehydrated.
For someone who already has difficulty maintaining circulation while upright, a hot shower, warm room, or hot outdoor environment can therefore make dizziness, tachycardia, weakness, fatigue, or brain fog more noticeable.
This does not mean that heat intolerance automatically indicates dysautonomia. Endocrine disorders, medications, dehydration, menopause, neurologic disease, and other conditions can also alter temperature tolerance.
Why can autonomic problems affect digestion?
The gastrointestinal tract depends heavily on coordinated neural regulation.
Autonomic and enteric nervous-system pathways help regulate movement through the stomach and intestines, secretion, blood flow, and communication between the digestive tract and central nervous system.
When these regulatory systems are disrupted, patients may experience nausea, early fullness, bloating, constipation, diarrhea, or altered gastrointestinal motility.
These symptoms are common and have many causes, so gastrointestinal complaints alone are not evidence of autonomic disease. The possibility becomes more relevant when digestive symptoms occur alongside other features such as orthostatic intolerance, abnormal sweating, heart-rate changes, or temperature dysregulation.
Can autonomic dysfunction contribute to brain fog?
Brain fog is not specific to autonomic dysfunction. Sleep disorders, medications, migraine, anemia, endocrine disease, infection, depression, nutritional deficiencies, and many other conditions can impair concentration and mental clarity.
However, some patients with orthostatic intolerance report that cognitive symptoms become more pronounced while standing or during prolonged upright activity.
Changes in circulation and the physiologic demands of maintaining an upright posture are among the mechanisms being investigated. This may help explain why some patients can think relatively clearly while lying or sitting but have more difficulty concentrating after standing, walking, showering, or performing prolonged activity.
How is autonomic dysfunction evaluated?
There is no single test that identifies every form or cause of autonomic dysfunction.
Evaluation begins with the symptom pattern and medical history. The timing of symptoms can be especially informative. A physician may ask whether symptoms occur after standing, meals, heat exposure, exercise, illness, or medications.
Heart rate and blood pressure may be measured while lying down and after standing. Depending on the clinical situation, evaluation may include an electrocardiogram, laboratory testing, cardiac assessment, neurologic examination, tilt-table testing, autonomic reflex testing, sweat testing, or evaluation for small-fiber neuropathy.
The goal is not simply to demonstrate that autonomic regulation is abnormal. An equally important question is why it is abnormal.
Other conditions can mimic autonomic dysfunction
Many symptoms attributed to dysautonomia are nonspecific.
Dehydration can produce tachycardia and dizziness. Anemia can cause fatigue, weakness, palpitations, and exercise intolerance. Thyroid disease can alter heart rate and temperature tolerance. Arrhythmias can cause palpitations or fainting. Medications can affect blood pressure, heart rate, sweating, and gastrointestinal function.
Adrenal disorders, nutritional deficiencies, vestibular disease, cardiac conditions, neurologic disorders, anxiety, and other illnesses may also produce overlapping symptoms.
That overlap is one reason it is important not to diagnose dysautonomia from a symptom list alone.
Treating the underlying illness and treating autonomic symptoms are different questions
When autonomic dysfunction is secondary to another disease, management often involves two related questions.
The first is whether an underlying condition can be identified and treated. The second is how to reduce the autonomic symptoms themselves.
Depending on the specific autonomic disorder and the patient’s medical circumstances, management may involve attention to hydration, salt intake when appropriate, compression garments, medication review, physical conditioning strategies, meal adjustments, temperature management, or medications directed at heart rate or blood pressure.
These approaches are not appropriate for every patient. For example, increasing sodium may be unsuitable for someone with certain cardiovascular, kidney, or blood-pressure conditions.
Treatment therefore depends on the type of autonomic dysfunction, its cause, accompanying medical problems, and which symptoms are most disabling.
Frequently Asked Questions
Can an infection affect the autonomic nervous system?
Yes. Autonomic dysfunction has been described during and after several infectious illnesses. Possible mechanisms vary and may include direct neurologic effects, toxins, inflammation, immune responses, or post-infectious changes. The presence of autonomic symptoms does not identify which infection, if any, is responsible.
What symptoms suggest autonomic nervous system dysfunction?
Possible symptoms include dizziness or fainting while standing, abnormal heart-rate responses, blood-pressure changes, altered sweating, heat intolerance, gastrointestinal motility problems, bladder symptoms, and exercise intolerance. These symptoms have many other possible causes and are not diagnostic by themselves.
Can you have autonomic dysfunction without low blood pressure?
Yes. Not every autonomic disorder produces orthostatic hypotension. Some patients have an excessive heart-rate increase with standing, while others experience orthostatic symptoms without dramatic changes in either heart rate or blood pressure during routine measurements.
Can autonomic dysfunction start after an illness?
Yes. Autonomic symptoms can develop during an illness or appear afterward. Post-infectious autonomic dysfunction has been studied particularly in post-COVID illness, although infections differ in their mechanisms and the evidence cannot automatically be generalized from one infection to another.
Can Lyme disease affect the autonomic nervous system?
Autonomic symptoms and dysautonomia have been reported in association with Lyme disease, and researchers have proposed autonomic dysfunction as one possible contributor to persistent symptoms in some patients. However, research remains limited, and dysautonomia has not been firmly established as a complication of Lyme disease in the medical literature. Other potential causes of autonomic symptoms should also be considered.
Clinical Takeaway
The autonomic nervous system helps coordinate heart rate, blood pressure, circulation, sweating, temperature regulation, digestion, bladder function, and other automatic processes. Because this regulatory network reaches throughout the body, illness-related autonomic dysfunction can produce symptoms that initially seem unrelated.
Infections are one of several possible contributors. Research into post-infectious conditions has strengthened evidence that measurable autonomic abnormalities can occur in some patients after illness, but the mechanisms and strength of evidence differ among diseases.
For patients with Lyme disease, autonomic dysfunction is an area of emerging interest rather than a settled explanation for persistent symptoms. The presence of dizziness, tachycardia, gastrointestinal symptoms, sweating changes, heat intolerance, or brain fog should prompt thoughtful evaluation rather than an assumption that every symptom has the same cause.
Recognizing an autonomic pattern can help connect symptoms across several body systems, but identifying the underlying reason for that pattern remains an essential part of the diagnosis.
Related Articles
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References
- Mayo Clinic Staff. Autonomic neuropathy: Symptoms & causes. Mayo Clinic.
- Carod-Artal FJ. Infectious diseases causing autonomic dysfunction. Clinical Autonomic Research. 2018;28(1):67-81.
- Golden EP, Bryarly MA, Vernino S. Dysautonomia: Diagnosis and management. Neurologic Clinics. 2023;41(1):193-213.
- Reis Carneiro D, Rocha I, Habek M, et al. Clinical presentation and management strategies of cardiovascular autonomic dysfunction following a COVID-19 infection: A systematic review. European Journal of Neurology. 2023;30(5):1528-1539.
- Camargo SM, dos Santos ALG, Maximo ST, et al. Assessing autonomic nervous system imbalance in long COVID-19 patients through heart rate variability during tilt testing. Scientific Reports. 2026.
- Adler BL, Chung T, Rowe PC, Aucott JN. Dysautonomia following Lyme disease: A key component of post-treatment Lyme disease syndrome? Frontiers in Neurology. 2024;15:1344862.
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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
