I have eyebags and I'm not sure if it's fluid retention, fat deposits, or allergies? 23 years old (Photo)

  Thank you for sharing your question. Your photographs show that you have prominent fat bags in the lower eyelids. These will often swell when lying down for a long time, if you are tired or if you have allergies. You require lower blepharoplasty. See an experienced surgeon for evaluation and discussion of treatment plan.Good luck,

You have some prolapsed fat of the lower lids.  This is a genetic issue, but allergies can aggravate it and cause the fat to swell.  You can have some HA filler such as Restylane injected below the fat in the tear trough.  This will help to smooth out the area and make the fat less noticeable.  It should last at least a year.  Your other option is a blepharoplasty surgery to reposition the fat and move it down into the tear trough.     

There are many causes of the appearance of bags and often fat
herniation, volume loss around the face and changes to the bone structure around
the eyes is the cause.

Some fat removal may improve the appearance of the
puffiness, but the surgeon would need to be careful not to remove too much fat
because it could make the eye look hollow.
When there is not a prominent cheek bone area, the bag looks prominent
in comparison. If surgery is performed, make sure the surgeon is aware to only
remove the amount of fat that looks puffy.

Very often replacing the loss of volume with injectable
fillers is the most common and most natural appearing technique we use to
improve the bags while making the whole face look better, more rested and
youthful.

I'll include a video which may help answer some of these
questions.

It appears that you have some fat herniation causing your appearance.  Its likely hereditary, your father or mother may have had a similar appearance at a younger age.  If you wish to have this corrected, you can have surgery (likely transconjuctival) or filler placed in the depression caused by the herniating fat.  I would recommend a consultation with an expert in either of those two procedures.  Wish you the best!  

Your pictures show infraorbital fat prolapse causing contour irregularity. Although lower eyelid blepharoplasty with fat preservation/redraping will smoothen the contours, you can also consider a less invasive approach with hyaluronic acid fillers (hyalu-blepharoplasty). The latest will camouflage the fat prolapse and improve the hollowness. It is not a permanent procedure but could delay the need for surgery. A consult with an Oculoplastic surgeon in NYC is recommended.