According to About.com, serous fluid is a normal, thin watery discharge that comes from a wound during its very early stages of healing. Typically, serous fluid appears between the first 48 to 72 hours after receiving a wound.
About.com points out that serous fluid is usually present in very small amounts. If there are large amounts of clear fluid forming around the incision line after a surgery, the development needs to be brought to the attention of a doctor. Although the fluid is normally clear, it is also sometimes yellowish in color. In some cases, serous fluid is able to escape the body through the skin even if there is no incision point or wound. This is common when an individual receives massive amounts of fluid.