eye rubbing and dark circles under eyes...allergies or something else?

hi! my 7 month old daughter used to get dark circles under her eyes when she was tired. now she's waking up with them and has them all day. rubbing her eyes often, too. i asked my pediatrician and her reply was 'could be allergies.' so, what do i do? how can i receive a better diagnosis? we have 4 indoor/outdoor cats. baby411 states early exposure to animals can be good. could this be seasonal allergies? could this be a sign of something more serious? thanks for any feedback and consideration to add a little more on this in the next edition. best, janine