Can a used tea bag treat puffy eyes?

Yes: Yes the active ingredient in tea is a vasoconstrictor which seems to reduce the redness and puffiness associated with baggy eyes.

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/