Yes, it sounds crazy, but it is recommended by some people as remedy of dark circles under eyes. Normally dark circles are caused discoloration from broken capillaries beneath skin under eyes. Toothpaste usually contains oil of ginger and peppermint. Apply a thin layer of the toothpaste under eyes and massage a little could effectively help promote blood circulation and remove blood stasis. You can apply some potato or cucumber slices to help too. Some people even recommend hemorrhoid cream as a remedy for dark circles, and it is actually works. There are still some other simple actions you could take right away. Drink a lot of water to moisturize your skin and avoid dehydration. Healthy diet is necessary. Quit smoking if you could. Last but also most important, good sleeping is essential for good skin. Take good sleep and you will find your skin is much better.