Could it be an allergic reaction to being in a dusty/dirty house? We were at IL's house last night (which isn't the cleanest), and DS started rubbing his eyes and getting all kinds of eye boogies and thick snot and dark eye circles not long after getting home. I gave him some Zyrtec, and this morning the whites of his eyes are a little pink, he has dark circles but his snot is clear again.
They have two dogs, but so do we. He's never reacted before, but our dogs are bathed regularly and our house is clean. FIL also smokes in the house, although he swears he doesn't. I'm taking him to the doctor this morning, and I know pink eye has been going around daycare, it just seems weird that all of this came on almost as soon as we got home last night.