What Sickness Causes the Body to Swell?: Understanding Edema and Underlying Conditions

September 28, 2025 •

4 min read

Swelling, or edema, is the medical term for puffiness caused by excess fluid trapped in the body's tissues. Understanding what sickness causes the body to swell is crucial for proper diagnosis and treatment, as this symptom can indicate anything from a minor issue to a serious underlying medical condition involving a major organ.

Quick Summary

Persistent or widespread body swelling can be a sign of a serious medical condition affecting major organs like the heart, liver, or kidneys. This fluid retention, or edema, often results from the body's inability to regulate fluids and can also be triggered by certain infections or lymphatic system issues.

Key Points

Edema is not a disease but a symptom: The term refers to swelling from excess fluid in body tissues, which is a sign of an underlying medical issue, not the illness itself.
Organ failure is a major culprit: Conditions like congestive heart failure, liver cirrhosis, and kidney disease are primary causes of fluid retention and swelling due to organ dysfunction.
Circulation problems cause localized swelling: Issues such as deep vein thrombosis (DVT) or chronic venous insufficiency can lead to swelling, most commonly in the legs and feet.
Lymphedema affects the lymphatic system: Damage to the lymph nodes, often from cancer treatment, impairs the body's ability to drain fluid, resulting in chronic swelling.
Seek professional medical attention for persistent swelling: Since edema can be a sign of serious health problems, it is crucial to consult a doctor for a proper diagnosis rather than self-treating.

Understanding Edema

Edema is the accumulation of excess fluid within the interstitial spaces, which are the gaps between the body's cells. While mild, temporary swelling can be caused by things like sitting for too long, a high-salt diet, or premenstrual hormonal changes, persistent or widespread edema is often a symptom of an underlying medical problem that requires professional medical evaluation. The location and severity of the swelling can provide clues about the root cause.

Heart Failure

One of the most common causes of body swelling is congestive heart failure. This condition occurs when the heart is unable to pump blood efficiently, causing blood to back up in the veins. This increased pressure forces fluid to leak out of the capillaries and into surrounding tissues, leading to swelling.

How heart failure leads to swelling:

Right-sided heart failure: When the right side of the heart struggles to pump, blood pools in the veins of the legs, ankles, and feet, causing peripheral edema. This can also lead to fluid accumulation in the abdomen, known as ascites.
Left-sided heart failure: If the left side of the heart is weak, blood can back up into the lungs. This can cause pulmonary edema, a serious condition where fluid fills the air sacs of the lungs, leading to shortness of breath.

Kidney Disease

Healthy kidneys are essential for filtering waste products and excess fluid from the blood. When the kidneys are damaged or diseased, they cannot perform this function effectively, resulting in a buildup of fluid and salt. This can cause swelling, particularly in the legs, ankles, and around the eyes.

Nephrotic Syndrome

Nephrotic syndrome is a specific kidney disorder that causes edema. It leads to damage in the tiny blood vessels (glomeruli) that filter waste, resulting in excessive protein loss in the urine. With less protein (albumin) in the blood to help hold fluid within the blood vessels, fluid can leak out into surrounding tissues.

Liver Disease and Cirrhosis

The liver produces albumin, a protein that maintains fluid balance in the body. Severe liver disease, such as cirrhosis, impairs the liver's ability to produce albumin. This lower level of blood protein leads to fluid leaking from blood vessels and accumulating in the abdomen (ascites) and legs.

Problems with the Lymphatic System

The lymphatic system is a network of vessels that collects excess fluid and waste from tissues and returns it to the bloodstream. If this system is damaged, for instance by cancer, infection, or surgery, it can lead to lymphedema. This is a chronic condition causing swelling, most often in the arms or legs.

Causes of Lymphedema

Secondary lymphedema: Most common, caused by damage from surgery (e.g., lymph node removal), radiation therapy, or infection.
Primary lymphedema: Rare and genetic, occurring due to an inherited condition affecting lymphatic system development.

Circulation and Blood Clot Issues

Poor circulation in the veins of the legs (venous insufficiency) or a blood clot can also cause swelling.

Deep Vein Thrombosis (DVT)

A DVT is a blood clot that forms in a deep vein, usually in the leg. This can block blood flow, causing sudden and often painful swelling in one leg. It is a medical emergency that requires prompt treatment to prevent the clot from traveling to the lungs.

Allergic Reactions and Infections

Allergic reactions and infections are a common cause of localized swelling, but severe cases can cause widespread swelling.

Severe allergic reactions (Anaphylaxis): A life-threatening reaction can cause rapid, widespread swelling, including the face, throat, and tongue. This is an emergency requiring immediate medical attention.
Infections: An infection like cellulitis, a bacterial skin infection, can cause localized swelling, redness, and warmth.

Medications and Other Factors

Several medications can cause fluid retention as a side effect, including high blood pressure medications, steroids, and NSAIDs. Other factors contributing to swelling include malnutrition, thyroid disease, and pregnancy.

Types of Edema Compared


Type of Edema	Primary Location	Common Causes	Key Characteristics
Peripheral Edema	Feet, ankles, legs, arms	Heart failure, kidney disease, venous insufficiency	Most common type; gravity can worsen swelling in legs
Pulmonary Edema	Lungs	Left-sided heart failure, kidney disease	Difficulty breathing, especially when lying down; requires urgent care
Cerebral Edema	Brain	Head trauma, stroke, infection, altitude sickness	Headache, confusion, vision changes; life-threatening
Macular Edema	Eye (macula)	Diabetes, blocked blood vessels in the retina	Blurry or wavy central vision; can lead to blindness if untreated

Conclusion: Seeking Medical Advice

Experiencing persistent or worsening swelling should prompt a visit to a healthcare professional. A thorough examination, including a medical history, physical assessment, and potentially further testing, is necessary to determine the underlying cause and the most appropriate course of treatment. While some causes of edema can be managed with lifestyle changes, such as a low-salt diet and regular exercise, others require specific medical interventions. Ignoring the symptoms of swelling can have serious consequences, especially if it indicates a progressive and potentially life-threatening condition like heart, liver, or kidney failure. Early diagnosis and management are key to preventing complications.

For more detailed information on edema and related conditions, consult the resources available from the National Institutes of Health.

Frequently Asked Questions

No, not all swelling indicates a serious illness. Minor swelling can be caused by factors like a high-salt diet, standing for long periods, or hormonal fluctuations. However, persistent, worsening, or widespread swelling warrants medical evaluation to rule out serious underlying conditions.

Swelling related to heart problems often affects both legs and ankles and can be accompanied by symptoms like shortness of breath, fatigue, and rapid heart rate. If you experience these symptoms, especially if swelling is persistent, seek medical advice.

Edema is a general term for swelling caused by excess fluid. Lymphedema is a specific, chronic type of edema caused by damage to the lymphatic system, which impairs its ability to drain fluids. Lymphedema often results in more persistent and severe swelling in a limb.

Yes, diet can contribute to swelling. A diet high in sodium causes the body to retain excess fluid, which can lead to bloating and swelling. In severe cases, extreme malnutrition can also cause edema due to a lack of protein.

Sudden swelling, particularly in only one leg, can be a symptom of a deep vein thrombosis (DVT), a potentially life-threatening blood clot. This is a medical emergency, and you should seek immediate medical attention.

Yes, several medications can cause swelling as a side effect. These include certain blood pressure medications, steroids, and nonsteroidal anti-inflammatory drugs (NSAIDs). Always consult your doctor before changing or stopping a prescribed medication.

Swelling combined with difficulty breathing, chest pain, a feeling of suffocation, or sudden swelling in a single limb (especially accompanied by pain) is a medical emergency. Also, if swelling occurs rapidly after a possible allergic exposure, seek immediate help.