I've had this problem for a few weeks now and it's just my left eye. Not sure what is causing it as I'm not using anything new. I did notice some dry scaly skin under my left eye so used a tiny bit of hydrocortisone for a few days and it cleared up. I went back to using retinol (which I've been using for over a year) and its flared up again slightly but I have no reaction under my right eye.
I drink lots of water, get an average of 6-7 hours sleep a night, sleep on my back or right side (as far as I know) and wear sunscreen every day. I've had to give up concealer too, my favourite makeup product as I have dark circles and am feeling rather blue about it.