Can there be a delayed reaction to a lip filler? (Photo)

If you have had this product injected in the past - unless you have had any medical changes since, you should not have a reaction from the product. Benadryl can assist to relieve some of the symptoms. If this persists over the next day I would recommend seeking the assistance of a dermatologist. All the best. 

The symptoms you describe are pretty classic for an urticarial (hive-like) allergic reaction.  In fact, larger, very swollen hives will often go from itching to burning/tenderness followed by oozing of yellow or clear fluid.  This occurs when people are allergic to bug bites and poison ivy too.  It is very unlikely that it is from Juvederm injected in May and much more likely from something you did in the past few days like take that new activated B supplement.  Benadry, other oral and topical antihistamines are helpful.  If you have any tongue or throat swelling, it could be more serious and needs urgent attention.  Either way, I recommend you stop that supplement and see a physician ASAP.