What's causing my left side to swell again after buccal fat pad removal? (Photo)

Great question!  There could be a few different reasons for this, but in the end this needs to be drained.  Depending on the nature of the drainage will provide your surgeon with the cause and then treatment can be provided.
Best of luck and hope this information helps!
- Dr. Roger Tsai  
Board Certified Plastic Surgeon

Infection and blockage of the parotid gland in the affected side are two of the most common possibilities for sub acute post surgical swelling. Both have different treatments. You should consider contacting your surgeon immediately and ask her/him to evaluate you in consultation ASAP 

Thank you for your pictures and questions. The appearance in the photo is concerning and you need to be evaluated by a physician as soon as possible. I would suggest seeing your plastic surgeon, your primary doctor, or an emergency department to be evaluated and treated. Best of luck!Dallas R. Buchanan, MD, FACSOwner & Board-Certified Plastic SurgeonVIVIFY plastic surgery

The likely cause of this is something to do with your spit gland or the parotid duct. Return to see your surgeon ASAP