Well, in my opinion, your eyes can not be swelling without any reasons. And generally speaking, there are many reasons which can lead to swelling eyes. But for your situation, I have to say that your eyes may suffer infection. In common, when your eyes have been infected by irritants, it can lead to swelling eyes, even at night. For the treatments, you can try some strawberry jam, which can be mixed with sterile water and then that can be used as a monthly enema. In that way, it can help with fluid retention as well as increasing colon health. Also, you can use cool used tea bags. And it can be effective too. Anyway, just be careful about it.
As far as i know, there are many reasons which can cause eyes swell, but the main reasons are subcutaneous fat, poor eating habits and nephropathy. In particular, the process of metabolism in our body will slow down at night, which makes it easier to give rise to swollen eyes. If the symptom relatively minor, just use the cotton with frozen milk and astringent to cover your eyes, after five to ten minutes, your puffy eye can be relieved obviously. However, if your symptom are very serious, you can eat more fresh fruits and vegetables with rich vitamins. Of course, the ice compress on your eye is a good way to relieve the tiredness of your eyes. In addition, the essential solution is not to drain too much water before you go to bed, or you can sleep in a higher pillow to reduce the chance of having swollen eyes.