I Got Sudden Bags/puffiness Under the Eyes? (photo)

If it is truly a sudden onset of bags then allergies are a possibility. Other possibilities include thyroid eye disease, though that's more gradual, or volume [water] retention due to kidney problems.

However, the most likely scenario is a sudden realization of a longstanding and gradual problem. Based on the photo, this looks like classic lower eyelid fat prolapse, however, an in person exam can better determine level of swelling.

If the condition happened suddenly it may be related to allergies or a thyroid imbalance.  If those are ruled out and you don't notice improvement you may consider cosmetic options.  Fillers are a non surgical temporary option to help disguise contour irregularities.  Lower blepharoplasty surgery is a more permanent solution to correct under eye concerns.  See a board certified plastic surgeon near you to learn more.

The fact that this has come suddenly does may me think more of a medical problem and I agree with the decision to see your primary MD ASAP to check some labs etc. If it is not medically or allergy related I would treat this with a lower lid transconjunctival blepharoplasty with fat transposition. You are young and you would do well with this procedure.Cost at my practice $ 3,500.Recovering is 2 wks but I prefer patients to prepare for 3 wks. Results are appreciated at about the 2-3 month mark.Hope this helps.Best of luck,DrC