Swollen Feet: What Causes Them? A Dermatologist Explains One-Sided vs Both-Sided Swelling, What Pitting Means, and Signs You Need the Hospital Right Away
Swollen feet (pedal edema) is a buildup of fluid in the tissue under the skin of the feet, ankles or shins, so that the shape of the foot changes, shoes feel tighter, and sock or strap marks look deeper than usual. The swelling itself is not a disease but a sign of many conditions with very different levels of urgency, from standing at work all day to a blood clot in a vein.
The question that sorts out the cause fastest is not "how swollen is it?" but is it one foot or both, does it pit when pressed, and is the skin there red and warm? These three questions separate nearly all the groups of causes before any blood test or ultrasound. This article explains how to read each sign, the medicines actually used for each cause, and the point at which you should stop watching it yourself and go to the hospital.
This article is written from a dermatologist's point of view, because one group of swollen feet starts in the skin itself, such as infectious cellulitis and venous rash, and these are the ones most often confused with other causes. For causes in the heart, kidney, liver or blood vessels, the article says which symptoms should be referred to which specialty.
How swollen feet happen: the mechanism behind every cause
Normally, fluid seeps out of the small blood vessels into the tissue and is drawn back into the veins and lymph vessels in a constant balance. Swollen feet appear when this balance is lost, and it can be lost in only four ways.
Higher pressure in the veins — blood does not return to the heart easily, so fluid is pushed out of the vessels. This occurs in heart failure, poorly working leg veins, and long periods of standing or sitting with the legs down.
Low protein in the blood — especially albumin, which holds water inside the vessels. When it falls, fluid leaks into the tissue. This occurs in kidney disease that loses protein in the urine, cirrhosis, and severe malnutrition.
Leakier vessel walls — from inflammation or infection, so that both fluid and protein escape together. This is the mechanism of cellulitis and of swollen allergic rashes.
Blocked lymph drainage — lymph vessels are damaged, blocked or removed, so lymph fluid stays behind. This occurs after lymph node surgery, after radiation, and after repeated skin infections.
These four different mechanisms leave different marks on the skin, which is why looking at and pressing on the foot tells you more than most people expect.
Three questions that sort out the cause of swollen feet fastest
Before getting to disease names, answer these three questions first, because they follow the same order a doctor uses at the bedside.
One foot or both — equal swelling on both sides usually comes from a whole-body cause: the heart, kidney, liver, medicines or habits. Swelling on one side usually comes from a local problem in that leg: infection, a clot, injury or the lymph system.
Does a dent stay after pressing — press with your thumb on the shin bone about 5 centimeters above the ankle, hold for 10 seconds and release. A lasting dent is called pitting edema and points to fluid from pressure or low protein. If it does not pit and the skin feels firm and rubbery, think of lymphedema and an underactive thyroid.
Is the skin there red, warm and tender — red, warm, tender skin on one side means infection or inflammation, which is the most urgent group and the group that dermatologists manage directly.
Answering these three takes under a minute, and it decides whether you should lie down with your legs up tonight or be in the hospital tonight.
How to do the pitting test yourself, and how to grade severity
Press with moderate force on the lower shin where there is bone underneath, not on the calf, which is muscle. Hold steady for 10 seconds, then look at the dent that remains.
Grade 1 — a dent about 2 millimeters deep that disappears within a few seconds.
Grade 2 — a dent about 4 millimeters deep that disappears within 10–15 seconds.
Grade 3 — a dent about 6 millimeters deep that lasts 1 minute or more. The foot and leg look clearly swollen.
Grade 4 — a dent deeper than 8 millimeters that lasts longer than 2 minutes. The leg is swollen until the skin is tight and shiny.
The grade does not tell you which disease it is, only how much fluid has built up, and you can compare it with yourself the next day to see whether it is better or worse. A more accurate method than judging by eye is to weigh yourself every morning after using the toilet, on the same scale. A rise of more than 1 kilogram in a day, or more than 2 kilograms in 3 days, is almost entirely water rather than fat, and is a sign to tell your doctor.
Quick table: what kind of swelling suggests what, and which doctor to see
Both feet, pitting, worse in the evening and gone by morning → poorly working leg veins, prolonged standing, salty food → general practitioner or internal medicine
Both feet, pitting, with breathlessness and being unable to lie flat → heart → cardiology, do not wait
Both feet, pitting, with a puffy face in the morning and foamy urine → kidney → nephrology
Both feet, with a growing belly and yellow eyes → liver → hepatology
Both feet, starting 2–8 weeks after a new medicine → drug side effect → the doctor who prescribed the medicine, never stop it yourself
One foot, red, warm, tender, with fever → infectious cellulitis → dermatologist or emergency room, today
One foot, calf pain and tightness, not clearly red → deep vein blood clot → emergency room, immediately
One foot, no pain, not red, slowly worsening over months, barely pits → lymphedema → dermatologist or vascular surgeon
Both feet, darkened skin, itch, scaling, chronic sores above the ankle bone → venous rash → dermatologist
Swollen feet on both sides from habits and surroundings
What it looks like — equal swelling on both sides, grade 1–2 pitting, worst in the evening and almost gone after a night's sleep, with no redness, warmth or pain.
Causes — standing continuously for more than 4–6 hours, sitting with the legs down for a long time, flights or bus trips longer than 4 hours, very hot weather that widens the vessels, sodium intake above 2,000 milligrams a day, and weight gain.
Severity and urgency — low, but never use it as a ready-made explanation. If the swelling does not go down at all after a full night's rest, something else is layered on top.
When to see a doctor — when the swelling is not gone by morning, when it reaches above the knee, or when breathlessness comes with it.
Swollen feet on both sides from heart, kidney and liver disease
This group is the reason swollen feet should never be assumed to be minor.
What it looks like — equal swelling on both sides, clear grade 2–4 pitting, slowly spreading up from the ankle to the shin and thigh. After lying down for a long time, the swelling may show in the lower back instead.
Causes — a weaker right side of the heart that lets blood back up, kidneys that leak protein or excrete less water and salt, and cirrhosis that makes less albumin while raising pressure in the portal system.
Severity and urgency — high. The accompanying signs to take seriously are: breathlessness lying flat so that you need more pillows, waking up gasping at night, tiring much faster than before, a puffy face and eyelids in the morning, fine foamy urine that does not clear, passing less urine, a belly that grows quickly, or yellow eyes and skin.
When to see a doctor — within a few days if you have any of the signs above, and immediately if you are so breathless that you cannot lie flat.
Treatment is aimed at the cause, not at the swelling. Loop diuretics such as furosemide and thiazide diuretics such as hydrochlorothiazide are commonly used in this group, but they must always be prescribed and monitored by an internal medicine doctor, because giving them to someone whose swelling has another cause can cause dehydration, worsen kidney function, and lower potassium enough to cause an abnormal heart rhythm. Never buy diuretics to take yourself for swollen feet, and never use leftover pills from someone at home. This is one of the most common and most dangerous mistakes with this symptom.
Swollen feet on both sides caused by medicines
Medicines are the most overlooked cause, because patients rarely connect a medicine taken for months with swelling that has only just started.
What it looks like — swelling on both sides with pitting, starting 2–8 weeks after a new medicine or a dose increase, without breathlessness.
Causes — calcium channel blocker blood pressure medicines, especially amlodipine, which causes ankle swelling in about 10–15% of people and is directly related to the dose · NSAID pain relievers such as ibuprofen and diclofenac · oral steroids such as prednisolone · estrogen and progesterone hormones · gabapentin and pregabalin · thiazolidinedione diabetes medicines such as pioglitazone
Severity and urgency — moderate. Not an emergency, but it needs to be fixed.
When to see a doctor — make an appointment with the prescribing doctor to review the medicines. Never stop blood pressure or heart medicines yourself, because that is far more dangerous than the swelling itself. The doctor may lower the dose, change the class, or add a medicine that reduces the swelling caused by the original one. Swelling from a medicine usually improves within 1–4 weeks after adjustment, which confirms that the diagnosis was right.
Swollen feet during pregnancy
What it looks like — swelling on both sides with mild to moderate pitting, commonly starting from the third trimester, worse in the evening and in hot weather.
Causes — blood volume rises by about 40–50% in a normal pregnancy, and the growing uterus presses on the large veins in the abdomen, so blood from the legs returns to the heart more slowly.
Severity and urgency — mostly a normal part of pregnancy, but there is a clear line.
When to see a doctor immediately — when swelling increases very quickly within one to two days, when the face and hands swell too, when there is a severe headache, blurred vision, flashing lights or tightness under the breastbone. This set of symptoms is preeclampsia, an obstetric emergency, and so is swelling in one leg with calf pain, because pregnancy raises the risk of blood clots several times over.
One swollen foot that is red, warm and tender is infectious cellulitis
This is the cause that AI and general health articles mention least, even though it is the cause dermatologists see most often among one-sided swollen feet.
What it looks like — a red, swollen patch on one side with a fairly clear edge, skin warmer than the other side when compared with the back of your hand, very tender to touch, sometimes with clear blisters or peeling skin on the red patch, and often a fever above 38 degrees Celsius, chills or marked tiredness for 1–2 days beforehand.
Causes — bacteria, especially streptococcus and staphylococcus, entering through a break in the skin. The most common entry point among Thai patients is a fungal infection between the toes, followed by small scrapes, cracked heels and picked ingrown nails.
Severity and urgency — high. It can spread within hours, and even faster in people with diabetes or weakened immunity.
When to see a doctor — today, not next week.
Treatment is oral antibiotics in mild cases. Commonly used ones are cloxacillin 500 milligrams four times a day or cephalexin 500 milligrams four times a day for 7–10 days. People allergic to penicillin are often given clindamycin 300 milligrams four times a day. The sign that it is working is that the fever comes down and the red edge stops spreading within 48–72 hours. If it is still spreading or the fever has not come down after 72 hours, go back to the doctor to review the diagnosis and consider injected antibiotics. The choice and dose of medicine are always the doctor's decision. Do not buy antibiotics to take yourself, because taking an incomplete course or stopping partway is the main cause of recurrence.
The thing that must be done alongside, and is often forgotten, is to cure the fungal infection between the toes as well, otherwise the entry point stays open and the infection will return. Repeated infections permanently damage the lymph vessels until lymphedema eventually develops. Read more at What is cellulitis? and how to tell it apart from erysipelas at How cellulitis and erysipelas differ.
One swollen foot with calf pain and tightness, but not clearly red, is a sign of a blood clot
What it looks like — swelling on one side that develops within a few days, with an aching or heavy pain in the calf more than in the foot. The calf on the swollen side measures more than 3 centimeters larger than the other when measured at the same level. The skin may look dark red or purple but is not very warm and the edge is not clear as it is in an infection. Some people see surface veins stand out more.
Causes — a blood clot in a deep vein (deep vein thrombosis). Risk factors are sitting still for more than 4 hours, recent major surgery or a cast, cancer, pregnancy and the period after childbirth, birth control pills and hormone replacement, and a family history of blood clots.
Severity and urgency — the highest in this article, because the clot can break off and block a blood vessel in the lung.
When to see a doctor — go to the emergency room immediately, and most urgently if there is sudden breathlessness, chest pain on deep breaths, palpitations or coughing up blood.
Do not massage, squeeze or apply heat to the calf of the suspected leg on the way to the hospital. Diagnosis uses a vein ultrasound together with a D-dimer blood test, and treatment is anticoagulant medicine, which only a doctor can prescribe.
One swollen foot with no pain, no redness, and slowly getting worse is lymphedema
What it looks like — swelling on one side that slowly increases over weeks to months, starting on the top of the foot and the toes. It barely pits or pits with difficulty, and the skin becomes thick and rubbery. The skin on top of the toes cannot be pinched into a fold, which is a sign specific to this condition. In later stages the skin becomes thick, bumpy, dry and flaky.
Causes — lymph vessels damaged or blocked. It occurs after lymph node removal in cancer patients, after radiation, after repeated cellulitis, from filariasis, and in some people from a congenital abnormality that shows up in the teenage years.
Severity and urgency — not an emergency, but the earlier care starts the better it can be controlled, because once the skin has thickened it is hard to reverse.
When to see a doctor — when one-sided swelling has not gone down at all after a night with the leg raised, and when you can no longer pinch the skin on top of the toes into a fold.
The main care is elastic bandaging or medical compression stockings at the pressure the doctor sets, lymphatic drainage massage by a specially trained physiotherapist, calf muscle exercises, and strict skin care to prevent repeated infection, because each infection damages the lymph vessels further. Diuretics are not a treatment for this condition and do not make it go down.
Swelling of both feet and legs with darkened, itchy, scaly skin is a venous rash
This condition is where blood vessel problems and skin problems meet, and it is the group most often misdiagnosed as a fungal infection or an allergic rash.
What it looks like — swelling on both sides, worse in the evening, with the skin above the inner ankle turning dark brown from red blood cells that have leaked out and collected. The skin is dry, itchy and scaly. Some people have hard skin tightening around the ankle so that the leg looks like an upside-down bottle, and in long-standing cases there may be shallow chronic sores above the inner ankle bone.
Causes — the valves in the leg veins do not close fully, so blood flows backward and the pressure in the small vessels stays high for a long time. It is common in people who stand for long hours at work, people with varicose veins, people who are overweight, and people who have had a blood clot in the leg before.
Severity and urgency — moderate. Not an emergency, but it is a chronic condition that can get worse if the pressure in the veins is not managed.
When to see a doctor — when the skin starts to darken, when there is chronic itching on both shins, and immediately when an open sore appears.
What truly treats this condition is lowering the pressure in the veins, with medical compression stockings at 20–30 mmHg in typical cases, put on from the moment you wake up before the legs swell, together with raising the legs above heart level 3–4 times a day for 20–30 minutes each time. The inflammation and itch are treated with a medium-strength steroid cream such as mometasone furoate 0.1% once a day for about 2 weeks together with a moisturizer twice a day, used consistently. What to avoid is applying antifungal cream because you think it is a fungal infection, which does not help and wastes time, as well as creams containing neomycin or fragrance, because the skin here develops contact allergy much more easily than skin elsewhere. Read more at Stasis dermatitis of the legs
Swollen feet after injury, and swollen feet from arthritis
What it looks like — swelling on one side that starts immediately or within a few hours of the event, with dark bruising following within 1–2 days, and tenderness at a specific spot over bone or tendon.
Causes — a twisted ankle, torn ligament, hairline fracture, and overuse.
The different case is gout — swelling, redness, warmth and severe pain at the base of the big toe, with pain peaking within 12–24 hours, so sore that even a blanket cannot touch it. It differs from cellulitis in that it stays limited to around the joint and often has a history of recurring attacks.
When to see a doctor — when you cannot put any weight on the foot, when the foot looks misshapen, when there is numbness or the toes are pale and cold, and when a joint is swollen, red and warm with a fever, because infectious arthritis must always be ruled out first.
Swollen feet in people with diabetes: why it is more urgent than for others
People with diabetes have three reasons why swollen feet carry more weight than in other people. First, damaged nerve endings mean they feel less pain than is really there, so wounds and infections are found late. Second, less blood reaches the toes, so wounds heal slowly and infection spreads quickly. Third, some diabetes medicines can themselves cause swelling.
In a person with diabetes, treat a swollen foot on one side that is red or warmer as an infection until proven otherwise, and see a doctor the same day. Another condition to think of is Charcot joint, in which the foot is swollen, red and warm without fever and with little pain. If treatment is delayed the foot becomes permanently deformed.
Swollen feet in older adults
In older adults there is usually not a single cause but several layered together: vein valves that wear out with age, calf muscles that act as the blood pump growing weaker from walking less, several regular medicines taken together, too little protein in the diet, and hidden heart or kidney disease.
One point to watch especially is sleeping sitting in a chair or wheelchair all day with the legs hanging down, which makes the swelling worse every day until the skin is tight, cracks and weeps fluid, which is the start of infection. Raising the legs to hip level or higher during the day and moving the ankles up and down in short sets many times a day genuinely help and cost nothing.
What the doctor checks when you come with swollen feet
The history and physical examination give more than half of the answer, and the remaining tests are chosen according to the working diagnosis.
Physical examination — comparing both sides, measuring calf circumference at the same level, the pitting test, looking at skin color and thickness, feeling the pulse on the top of the foot, listening to the lungs and heart, and examining the abdomen and liver.
Blood tests — kidney function and electrolytes, albumin, liver function, thyroid hormone, BNP or NT-proBNP when the heart is suspected, and D-dimer when a clot is suspected.
Urine test — looking for protein leak, which is an inexpensive test that gives a lot of information in the both-sided group.
Imaging — leg vein ultrasound when a clot or leaking vein valves are suspected, X-ray when a bone problem is suspected, and an echocardiogram when the heart is suspected.
What you can do yourself while waiting to see a doctor, and what to avoid
What genuinely helps in the group that is neither infection nor blood clot
Raise the legs above heart level 3–4 times a day for 20–30 minutes each time, with the heels higher than the chest, not just resting on a low stool.
Move the ankles up and down slowly 20 times per round, every hour you must sit for a long time. The calf muscles are the pump that pushes blood back to the heart.
Reduce sodium to below 2,000 milligrams a day. The main sources in Thai food are fish sauce, soy sauce, stock cubes, instant noodles and processed foods.
Wear medical compression stockings from the moment you wake up, before the legs start to swell, but people with arterial disease or diabetes must have a doctor check the pulses in their feet first.
Weigh yourself every morning and write it down so that the doctor can see the trend.
What to avoid
Do not buy diuretics to take yourself — the danger is dehydration and abnormal electrolytes.
Do not massage or apply heat to a leg that might have a blood clot.
Do not wrap an elastic bandage tightly overnight by yourself, especially if the pulse in the feet is weak, because it may leave the toes without enough blood supply.
Do not stop blood pressure or heart medicines yourself even if you suspect they are the cause. Talk to the doctor who prescribed them.
Do not puncture or cut tight, weeping skin to drain the fluid, because it opens a direct way in for infection.
Warning signs that need the hospital immediately
Swelling of one foot or leg that comes on fast within 1–2 days, with calf pain and tightness
Sudden breathlessness, chest pain on deep breaths, palpitations, or coughing up blood
Red, warm swelling that spreads quickly with a fever above 38 degrees Celsius, or chills
Pain far out of proportion to what can be seen, dark purple skin, blood-filled blisters, or a crackling feel under the skin
Unable to lie flat and needing to sit up to breathe comfortably, or waking up gasping at night
Passing much less urine, or no urine at all in a day
In pregnancy, rapid swelling of the face and hands, severe headache, blurred vision, or pain under the breastbone
Toes that are pale, cold or numb, or a pulse on the top of the foot that cannot be felt
When to see a dermatologist rather than wait and watch
Swelling on one side with skin that is red, warm or tender, whether or not there is a fever
Skin on the shins and ankles that darkens, itches, scales, or starts to have shallow sores above the ankle bone
Skin that is swollen tight until it cracks and weeps fluid
Cellulitis in the same leg more than 2 times in one year, which usually means an entry point is still untreated, such as a fungal infection between the toes or in the nails
Skin on top of the toes that can no longer be pinched into a fold
A fungal infection between the toes or deep cracked heels together with a swollen leg, which is the set of problems that leads to repeat infection. See how to manage them at What causes peeling feet? and What causes athlete's foot (water-bite feet)?
See other skin condition topics at the skin conditions index
Short summary
Swollen feet are fluid trapped in the tissue. It is not a disease but a sign whose urgency varies greatly with the cause.
The questions that sort out the cause fastest are: one foot or both, does it pit when pressed, and is it red and warm?
Equal swelling on both sides usually comes from the whole body: heart, kidney, liver, medicines or habits. Swelling on one side is usually a local problem of that leg.
One-sided swelling that is red, warm and tender is infectious cellulitis. It needs antibiotics, and the fungal infection between the toes, which is the entry point, must be treated at the same time.
One-sided swelling with calf pain and tightness without clear redness is a blood clot until proven otherwise. Do not massage it. Go to the emergency room.
Darkened, itchy, scaly skin above the ankle with swelling on both sides is a venous rash, which is treated by lowering the pressure in the veins, not with antifungal medicine.
The one thing to do right away is to look at whether the swelling is on one side or both. If it is one side and there is redness, warmth or calf pain, go to the hospital today. For both-sided swelling with no warning signs, raise the legs, cut down on salt, write down your weight every morning, and make an appointment to find the cause.
Frequently asked questions
Are swollen feet dangerous?
It depends on the kind of swelling. Mild swelling of both feet in the evening after standing or sitting all day that is gone after one night is mostly not dangerous. But three patterns are genuinely dangerous: swelling of one foot with calf pain and tightness, which may be a blood clot that can travel to the lungs; swelling of one foot that is red, warm and tender with a fever, which is an infection that can spread within hours; and swelling of both feet with breathlessness so bad that you cannot lie flat, which points to the heart. In addition, a pregnant woman whose face and hands swell quickly together with a headache or blurred vision has an emergency. In short, do not judge by how much it swells, but by whether it is one foot or both and what symptoms come with it.
What kind of swollen feet means kidney disease?
Swollen feet from kidney disease are usually equal on both sides with clear pitting, and the feature that sets it apart from other causes is swelling of the face and eyelids when you wake up in the morning, which then moves down to the feet by evening after you have been up and about all day. Accompanying signs that help confirm it are fine foamy urine that does not clear quickly, passing less urine, higher blood pressure, tiredness, poor appetite and paleness. A quick and inexpensive way to confirm it is a urine test for protein leak together with blood tests for kidney function and albumin. If you have this set of symptoms, see an internal medicine doctor within a few days and do not wait for months.
How do I get rid of swollen feet?
You have to work out what is causing the swelling first, because what helps in one group may not help or may be dangerous in another. In the group with swelling from habits or leg veins, what genuinely works is raising the legs above heart level 3–4 times a day for 20–30 minutes each time, moving the ankles up and down 20 times every hour you sit for a long time, wearing medical compression stockings from the moment you wake up, cutting sodium below 2,000 milligrams a day, and losing weight if overweight. For swelling from the heart, kidney or liver, treatment is of the underlying disease by a doctor, and for infection it is antibiotics. What to avoid in every group is buying diuretics to take yourself, because they cause dehydration, worsen the kidneys and upset electrolytes.
What causes swollen feet in older adults?
In older adults there is usually not one cause but several at once. The most common is leg vein valves that wear out with age, together with walking less so that the calf muscles, which pump blood back to the heart, weaken. Next come side effects of several medicines taken together, especially calcium channel blocker blood pressure medicines and NSAID pain relievers, then heart and kidney disease that may not yet have been diagnosed, and too little protein in the diet. A habit that clearly makes it worse is sitting or sleeping with the legs down on a chair all day. They should see a doctor to review all their medicines and have basic blood and urine tests, especially if the swelling keeps increasing or is on one side only.
What causes swollen feet on one side without pain?
For swelling on one side without pain or redness that slowly increases over weeks to months, think first of lymphedema. Clues are that it barely pits, the skin becomes thick and rubbery, and the skin on top of the toes cannot be pinched into a fold. Causes include having had lymph node removal, having had radiation, having had repeated skin infections in that leg, or filariasis. Other causes to rule out are a blood clot, which in some people is also not clearly painful, especially if the swelling came on quickly within a few days, and leaking vein valves in that leg alone after an earlier clot. See a doctor for a vein ultrasound, and do not conclude by yourself that no pain means no danger.
What causes red swollen feet?
For red swelling of the foot or leg, tell apart three main things. One is infectious cellulitis, which is a red patch on one side with a fairly clear edge, warmer than the other side when compared with the back of your hand, very tender, usually with a fever, and spreading wider within hours to days. Two is gout, which has red, warm, severe pain only around a joint, especially the base of the big toe, peaking within 12–24 hours, and usually with earlier attacks. Three is a venous rash, which is dark reddish brown, on both sides, itchier than it hurts, and chronic over months. If you cannot tell them apart, treat it as an infection until proven otherwise and see a doctor that day, especially in people with diabetes or weakened immunity.
References
Trayes KP, Studdiford JS, Pickle S, Tully AS. Edema: diagnosis and management. American Family Physician.
Ely JW, Osheroff JA, Chambliss ML, Ebell MH. Approach to leg edema of unclear etiology. Journal of the American Board of Family Medicine.
Raju S, Neglén P. Chronic venous insufficiency and varicose veins. New England Journal of Medicine.
Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections. Infectious Diseases Society of America.
Sullivan RJ, et al. Diagnosis and treatment of lymphedema. Journal of the American Academy of Dermatology.
Clinical Practice Guideline on Venous Thromboembolism, Thai Society of Hematology
Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed September 18, 2026
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