Puffy eyes in the morning. under eyes. why?

Swelling: Either an allergy with puffiness, or swelling from excess fluid in your system which only accumulates under the eyes after lying flat all night. It then resolves after you are seated or standing in the morning, and the fluid shifts to a more dependent area. If you sleep with your head more elevated, rather than flat, you may find this to be less of a problem.

Puffy Eyes: Puffy or swollen eyes can be caused by fluid retention, stress, allergies, hormone changes, and other factors. Other times we get puffy eyes after sleeping. This can be caused by too much sodium in the diet, which causes water retention. Puffy eyes can also be caused by lack of sleep or excessive alcohol intake. http://www.eyehealthweb.com/puffy-eyes/