CNN - Dr. Joshua Zeichner: "What Causes Dark Under-Eye Circles?"
Blue circles result from oxygenated blood pooled beneath the under-eye skin.
Skin here is very thin and almost transparent, so blood shows through. "As we get older, we lose subcutaneous fat, which can mask blueness below the surface of the skin," says dermatologist Dr. Joshua Zeichner, the director of cosmetic and clinical research at The Mount Sinai Medical Center. Learn more