Lips Randomly Swell After Belotero? (photo)

I had belotero lip filler about two months ago. After the initial swelling went down (7-10 days) everything looked great and was fine. However since then about once a week I wake up with a swollen lip (or sometimes just a small section) of lip swollen. It goes away with ice and a little time but am wondering if this is an allergic reaction to the filler? I know it is not related to food allergies or new products for my lips. The swelling is often excessive but does disperse after a few hours.