Most Helpful Girl
Depends. There are many different kinds. Sometimes it is genetic due to discolored pigment which can probably even be treated with a cosmetic laser procedure. Other times it is due to the shape and depth of your eyes, in this case there isn't much that can be done but you can use a good concealer. Make Up Forever makes an amazing waterproof concealer that does wonders for me, I recommend it. You can buy it at a Sephora store.
Sometimes it is just due to lack of sleep..in that case try to sleep more. Lack of sleep will always aggravate dark circles but some people are more prone to have them than others. I'm fairly prone so when I don't sleep my undereyes look like crap, but other people who aren't prone only have a slight shadow under their eyes from not sleeping.