However, if you've never sought treatment for your allergies, why not talk to your health care provider, or consult with an allergist, about your allergies. Pronounced undereye circles are often passed down, genetically, within families. Maybe you can look through old family photos to see if you can find a pattern of inheritance. Another likely culprit is the skin directly under the eyes, which is just about the thinnest skin you can find on your body. Rubbing your eyes excessively can make the dark circles worse.
Dehydration can also make the circles more obvious.
If you normally don't drink much water, perhaps you can add a few more glasses to your daily liquid intake.