Fluid retention (oedema) occurs when fluid isn't removed from the body tissues, including the skin. Causes include the body's reaction to hot weather, a high salt intake, and the hormones associated with the menstrual cycle. Symptoms include swelling of body parts such as feet, hands and ankles, a feeling of stiffness or aching and weight fluctuations. Drinking plenty of water will actually help your kidneys to flush out excess fluid. Fluid retention may be a sign of disease.