Oedema is swelling caused by excess fluid trapped in the body’s tissues. It most commonly affects the feet, ankles and legs, but can appear in other parts of the body including the hands, face and abdomen. While mild swelling often goes away on its own, persistent oedema may signal underlying health conditions that need medical attention.
Understanding Oedema
Oedema, also spelled edema, occurs when fluid leaks from small blood vessels into nearby tissues, causing them to swell. This fluid buildup happens when the normal balance between fluid moving into and out of tissues becomes disrupted. The lymphatic system, which is a network of tubes throughout the body, normally drains this fluid from tissues and returns it to the bloodstream. When this system cannot keep up with the fluid accumulation, or when too much fluid is leaking from blood vessels, swelling becomes visible and noticeable.[1][2]
The swelling can affect just one part of the body, known as localised oedema, or it can involve multiple areas throughout the body, called generalised oedema. The most common form is peripheral oedema, which affects the extremities, particularly the lower legs, ankles and feet. This happens partly because of gravity, as fluid naturally pools in the lower parts of the body when standing or sitting for long periods.[3]
How Common Is Oedema
Oedema is a widespread condition, though the exact number of people affected is difficult to determine because mild cases often resolve without medical intervention. The condition is particularly common among certain groups. Pregnant women frequently experience swelling in their legs and feet due to hormonal changes and increased pressure from the growing uterus on blood vessels. Adults aged 65 and older are also more likely to develop oedema, as age-related changes in circulation and the increased likelihood of underlying health conditions make fluid retention more probable.[10]
Because oedema can result from many different causes, ranging from simple lifestyle factors to serious diseases, it affects people across all age groups and backgrounds. Some people experience temporary swelling after long flights or hot weather, while others deal with chronic oedema related to ongoing health conditions. The condition affects both men and women, though women may experience it more frequently during certain life stages, particularly pregnancy and the weeks before menstruation.[2][16]
What Causes Oedema
The underlying causes of oedema are varied and can range from simple, harmless situations to serious medical conditions. Understanding what triggers fluid buildup helps in determining the appropriate response and treatment. Oedema develops when the delicate balance of fluids in the body is disturbed by changes in blood vessel pressure, protein levels in the blood, or the ability of the lymphatic system to drain fluid effectively.[1]
One of the most basic causes is prolonged standing or sitting in one position. When you remain still for extended periods, gravity pulls fluid down into the legs and feet, where it accumulates in the tissues. This is why many people notice swollen ankles after a long flight or a day spent mostly sitting or standing at work. Hot weather also contributes to oedema, as the body becomes less efficient at removing fluid from tissues when temperatures rise.[2]
Several serious medical conditions can cause oedema as one of their symptoms. Congestive heart failure occurs when the heart becomes too weak to pump blood effectively throughout the body. This causes blood to back up in the veins, increasing pressure and forcing fluid out into the surrounding tissues. People with heart failure may notice swelling in their legs, ankles and sometimes their abdomen. In severe cases, fluid can accumulate in the lungs, creating a life-threatening condition called pulmonary oedema.[1][8]
Kidney disease leads to fluid retention because damaged kidneys cannot remove enough sodium and water from the body. As these substances build up, pressure increases in blood vessels, causing fluid to leak into tissues. People with kidney problems often develop swelling around the eyes as well as in the legs. Liver disease, particularly cirrhosis, causes oedema through multiple mechanisms. The damaged liver cannot produce enough proteins that help keep fluid in blood vessels, and it also creates increased pressure in blood vessels, leading to fluid accumulation, especially in the abdomen and legs.[4][6]
Venous insufficiency is another common cause, occurring when the valves in leg veins become weakened or damaged. These valves normally help blood flow back up to the heart against gravity. When they fail, blood pools in the lower legs, increasing pressure and forcing fluid into the surrounding tissue. This often leads to swelling that worsens throughout the day and may be accompanied by skin changes and varicose veins.[3]
Certain medications can trigger oedema as a side effect. Blood pressure medications, particularly calcium channel blockers, can cause swelling in the legs and feet. Other drugs that may lead to fluid retention include some pain medications, steroids, hormonal treatments including birth control pills and hormone therapy, and certain antidepressants. If medication is causing swelling, a healthcare provider may adjust the dosage or switch to a different drug.[2][4]
Who Is at Higher Risk
Several factors increase the likelihood of developing oedema. People who spend long hours standing or sitting in one position for work are more prone to leg and ankle swelling. This includes healthcare workers, retail employees, office workers, and anyone whose job requires staying in one position for extended periods. The immobility prevents the normal pumping action of leg muscles that helps push blood and fluid back up toward the heart.[2]
Being overweight or obese significantly increases the risk of oedema. Excess body weight puts additional pressure on blood vessels, particularly in the legs, making it harder for blood and fluid to circulate properly. Weight also contributes to other health conditions that can cause oedema, such as heart disease and diabetes.[2][4]
Pregnant women are at particularly high risk, especially during the later stages of pregnancy. The growing uterus puts pressure on the large blood vessels in the pelvis and abdomen, slowing blood return from the legs and causing fluid to accumulate in the lower extremities. Hormonal changes during pregnancy also encourage the body to retain more fluid. While some swelling is normal during pregnancy, sudden or severe swelling, particularly in the face and hands, may indicate a serious condition called preeclampsia and should be reported to a healthcare provider immediately.[2][16]
Older adults face increased risk of oedema for several reasons. Age-related changes in blood vessel function, decreased physical activity, and the higher likelihood of having chronic health conditions all contribute to fluid retention. Additionally, older people are more likely to take medications that can cause swelling as a side effect.[10]
People with a history of heart disease, kidney disease, liver disease, or diabetes are at higher risk of developing oedema. Those who have had previous blood clots, particularly deep vein thrombosis in the legs, may experience chronic swelling. Cancer patients, especially those who have undergone surgery or radiation therapy that affected lymph nodes, are at risk of developing lymphoedema, a specific type of swelling caused by damage to the lymphatic drainage system.[4][11]
Dietary habits also play a role in risk. People who consume large amounts of salt in their diet are more likely to retain fluid. Salt causes the body to hold onto water, which can lead to swelling, particularly in those who are already prone to oedema due to other factors. Poor nutrition, especially diets lacking adequate protein, can lead to low levels of albumin in the blood, a protein that helps keep fluid inside blood vessels.[2][8]
Signs and Symptoms
The most obvious symptom of oedema is visible swelling in the affected area. The swelling occurs when fluid accumulates in tissues, causing them to expand and appear puffy. Most commonly, this affects the feet, ankles and legs, but it can also develop in the hands, arms, face, or abdomen. The swollen area typically looks larger than usual and may feel tight or uncomfortable.[1]
The skin over swollen areas often appears stretched, shiny, and smooth. This happens because the accumulated fluid pulls the skin tight over the underlying tissue. In some cases, the skin may feel warm to the touch, particularly if the swelling is related to inflammation or infection. The colour of the skin may also change, appearing reddish or having an unusual discoloration.[2]
A distinctive characteristic of many types of oedema is called pitting. When you press your finger firmly into the swollen area for a few seconds and then release, a dimple or indentation remains in the skin for a short time before slowly filling back in. This pitting occurs because the fluid is being temporarily pushed aside by the pressure. Not all oedema causes pitting, however. Some types, particularly lymphoedema, cause non-pitting swelling where the skin springs back immediately after being pressed.[1][10]
People with oedema often report a feeling of heaviness in the affected body part. Swollen legs can feel weighted down, making walking more difficult and tiring. The swelling can also cause stiffness in joints, making it harder to move the affected area normally. Clothing, shoes, and jewellery may feel tight or uncomfortable, and may leave marks or indentations on the skin.[1][2]
Some people experience mild pain or achiness in swollen areas, though oedema itself is not always painful. Discomfort is more common when swelling develops quickly or becomes severe. If the swelling is related to an underlying condition like venous insufficiency, there may be additional symptoms such as skin discolouration, particularly a brownish tint around the ankles, or the development of open sores or ulcers on the legs.[2][7]
Weight gain can occur with oedema, sometimes quite rapidly. If fluid is accumulating throughout the body, a person may gain several pounds over just a few days. This rapid weight change, combined with visible swelling, often indicates a more serious underlying problem that requires medical evaluation. In contrast, unexplained weight fluctuations may also accompany oedema.[1]
When oedema affects the abdomen, the belly may appear noticeably larger and feel full or tight. This type of swelling, called ascites, is often related to liver disease or heart failure. If fluid accumulates in the lungs, symptoms become more severe and include shortness of breath, difficulty breathing when lying down, coughing, and a feeling of suffocation. This is a medical emergency requiring immediate attention.[6]
Preventing Oedema
While not all cases of oedema can be prevented, particularly those caused by underlying medical conditions, several lifestyle measures can help reduce the risk or severity of fluid retention. Movement and regular physical activity are among the most important preventive strategies. When you move around, your leg muscles contract and squeeze the veins, helping to push blood and fluid back toward the heart. This natural pumping action prevents fluid from pooling in the lower legs. Even gentle exercise like walking can significantly improve circulation and reduce swelling.[2]
If your work requires prolonged standing or sitting, taking regular breaks to move around is essential. Standing workers should try to sit periodically, while those who sit should stand and walk every hour or so. When seated, avoid crossing your legs, as this position can restrict blood flow. Simple exercises like ankle rotations, heel raises, and flexing the feet up and down can be done while sitting or standing and help keep fluid moving.[2][23]
Elevating the legs above the level of the heart when resting helps gravity drain accumulated fluid from the lower extremities. This can be done by lying down and propping the legs up on pillows, or by using a footstool to raise the feet while sitting. Doing this for 15 to 30 minutes several times a day can prevent or reduce swelling, particularly at the end of the day.[2]
Dietary changes play a significant role in preventing fluid retention. Reducing salt intake is particularly important, as sodium causes the body to retain water. This means limiting processed foods, fast food, canned goods, and packaged meals, which typically contain high levels of salt. When cooking at home, use herbs and spices for flavour instead of adding salt. Reading nutrition labels helps identify high-sodium products to avoid.[2][13]
Staying well-hydrated might seem counterintuitive when dealing with fluid retention, but drinking plenty of water actually helps. When the body is dehydrated, it responds by retaining more fluid. Adequate hydration signals the body that it is safe to release excess fluid. Aim for at least eight glasses of water daily, and avoid excessive alcohol consumption, which can contribute to dehydration and swelling.[13]
Maintaining a healthy weight reduces pressure on blood vessels and decreases the risk of conditions that cause oedema, such as heart disease and diabetes. If weight loss is needed, a gradual approach combining healthy eating and regular physical activity is most effective and sustainable.[2]
Wearing appropriate clothing and footwear matters too. Tight clothes, socks with elastic bands, and restrictive shoes can compress blood vessels and prevent proper circulation. Choose comfortable, loose-fitting clothing and supportive shoes with good cushioning. For people at risk of leg swelling, compression stockings can be helpful. These specially designed garments apply graduated pressure to the legs, with the greatest pressure at the ankle and gradually less pressure moving up the leg. This helps squeeze fluid out of the tissues and back into the bloodstream. Compression stockings should be put on first thing in the morning before swelling develops.[2][9]
Good foot and skin care helps prevent complications. Keeping the skin clean, dry, and moisturised reduces the risk of infection in swollen areas. This is particularly important for people with diabetes or venous insufficiency, who are more prone to developing skin problems and ulcers. Inspect the skin regularly for any breaks, sores, or colour changes.[2]
How the Body Works and What Goes Wrong
To understand oedema, it helps to know how fluid normally moves in the body. Blood vessels, particularly tiny vessels called capillaries, constantly exchange fluid with the surrounding tissues. The pressure inside blood vessels, called hydrostatic pressure, pushes fluid out through the vessel walls into the tissues. At the same time, proteins in the blood, especially one called albumin, create a pulling force called oncotic pressure that draws fluid back into the blood vessels. Under normal circumstances, these forces balance each other, and any excess fluid in the tissues is collected by the lymphatic system and returned to the bloodstream.[3][6]
Oedema develops when this delicate balance is disrupted. If pressure inside blood vessels increases, more fluid is pushed out into the tissues than can be reabsorbed. This happens in conditions like heart failure, where blood backs up in the veins because the heart cannot pump effectively. The increased venous pressure forces fluid out of the capillaries and into the surrounding tissue.[6]
Another mechanism involves the oncotic pressure. When blood protein levels, particularly albumin, are too low, the pulling force that keeps fluid inside blood vessels weakens. Without adequate protein to hold it in place, fluid leaks out into the tissues more easily. This occurs in kidney disease when protein is lost through urine, in liver disease when the damaged liver cannot produce enough protein, or in severe malnutrition when protein intake is insufficient.[4][8]
The walls of blood vessels can also become more permeable, or leaky, allowing fluid to escape more easily. This happens during inflammation, allergic reactions, and infections, when chemical signals cause the walls of capillaries to open up. While this increased permeability helps immune cells reach sites of infection or injury, it also allows more fluid to leak into tissues, causing swelling.[8]
The lymphatic system plays a crucial role in preventing oedema by draining excess fluid from tissues. When lymph vessels are damaged or blocked, fluid accumulates because it has nowhere to go. This creates lymphoedema, which has different characteristics than other types of oedema. Lymph vessels can be damaged by surgery, particularly when lymph nodes are removed during cancer treatment, by radiation therapy, by infections, or by tumours that block lymphatic drainage.[11]
In venous insufficiency, the one-way valves in leg veins that normally prevent blood from flowing backward become damaged or weakened. When these valves fail, blood pools in the legs rather than returning efficiently to the heart. The pooled blood increases pressure in the leg veins and capillaries, forcing fluid out into the surrounding tissue. Over time, chronic venous insufficiency can cause permanent changes in the skin and underlying tissue.[3]
Sodium retention directly contributes to fluid retention because water follows sodium. When the kidneys retain more sodium than normal, either because of kidney disease or hormonal signals, the body must also retain water to maintain the proper concentration of sodium in the blood. This extra water increases blood volume and pressure, leading to oedema. Similarly, when dietary salt intake is high, the body retains more water to dilute it, potentially causing swelling.[8]
Hormonal changes, particularly those involving oestrogen and progesterone, can cause fluid retention. These hormones affect how the kidneys handle sodium and water. This explains why many women experience swelling before their menstrual periods, during pregnancy, or when taking hormonal medications. Pregnancy also causes oedema through additional mechanisms, including increased blood volume and pressure from the growing uterus on major blood vessels in the pelvis and legs.[3]
