Puffy eye, on waking up in the morning is a very widely reported condition. The problem is not very serious in many cases, especially if the problem goes away during the day. The fundamental mechanism that is causing your eyes to puff up, is known as an edema in medical circles. To be very exact, it is called periorbital edema. This is basically a fluid accumulation in the tissues under the eyes.
There are a number of simple reasons as to why this problem occurs. Curiously, both oversleeping and deficient sleep can cause this problem. When you go to sleep, there is a hormone that is secreted in your body that tells your kidneys to shut down and not create urine. If it were not for this hormone, adults would be bedwetting as much as children do. Incidentally, children tend to wet the bed because this hormone is not as pronounced as it is in adults. With the kidneys being switched off for the night, the fluid in the body starts to accumulate. When we are awake, we are generally in a standing position and most of the fluids in our tissues tend to follow gravity but with a proper action of the vascular system, this fluid accumulation is kept in check. However, you do tend to notice how sitting in a position for a very long time causes your feet to swell up. When you are sleeping, the accumulation of fluid happens all over your body and your whole body swells up, an effect that is most visible in the thin tissues below the eyes. Water retention itself can be caused by thyroid problems, excess salt in the diet, deficient coffee intake, and even too much fluid intake before going to bed.
Treating puffy eyes requires that you keep your sleep timings standard so that you avoid oversleeping or not sleeping enough. A standard seven to eight hours is a good measure. Beyond that, you must also try to sleep with your head in a more elevated position that you have right now to avoid fluid pooling near your eyes. It is also important to reduce the amount of salt in your diet, as excess salt requires more water in the body and if this is not excreted your are dealing with an abnormal amount of fluid in the body. Treating a puffy eye immediately after waking can be done by simply apply some cold water over the eyes and rubbing them. Also increase your intake of the vitamins A, C and E by supplements as a deficient intake can be reflected in puffy eyes.