Fluid retention under eyes or bags under eyes can be due to -
- diet related - excessive salt intake
- hormonal imbalance - hypothyroid
- Oversleeping/sleep deprivation - Interrupted sleep cycles are common causes of eye puffiness
- alcohol and tobacco use - Alcohol and tobacco contain toxins that may lead to stress, fatigue, and hormonal changes. These can cause fluid retention and swelling around the eyes in some people
- allergies - chronic allergies can cause leakage of fluid from small blood vessels into the surrounding tissue. SInce you have sinusitis, this can be a possible cause in your case.
- skin allergies or dermatitis
- normal aging phenomenon, seen sometimes early in some people
I would advise you to consult your doctor to rule out problems like hypothyroid. In the meantime cut down on added salt, alcohol/tobacco etc.