Swelling (also called edema or oedema) is an abnormal buildup of fluid in the tissues, causing noticeable enlargement, puffiness, or distension of a body part such as the legs, ankles, feet, hands, face, abdomen, or joints. It often feels soft, doughy, or tight to the touch and may leave a temporary indentation (pitting) when pressed with a finger in many cases. Common localized causes include injury/trauma (e.g., sprains, fractures, or insect bites with inflammation), infections (e.g., cellulitis causing red, warm, tender swelling), venous problems (e.g., varicose veins or deep vein thrombosis with unilateral leg swelling), lymphatic obstruction (lymphedema after surgery or radiation), or allergic reactions (angioedema with rapid facial/lip/tongue swelling). Generalized or bilateral swelling frequently stems from heart failure (often worse in lower extremities and at end of day), kidney disease (e.g., nephrotic syndrome with protein loss leading to low blood oncotic pressure), liver cirrhosis (with ascites in the abdomen and leg edema), low protein levels (malnutrition or malabsorption), medications (e.g., calcium channel blockers, steroids, NSAIDs), prolonged immobility, pregnancy (due to hormonal changes and pressure on veins), or thyroid issues (myxedema in hypothyroidism with non-pitting facial/eyelid swelling). It can be acute (sudden onset) or chronic, mild to severe, and may accompany pain, redness, warmth, shortness of breath, weight gain from fluid retention, or skin changes depending on the underlying cause.