4 weeks post Botox in glabella and above each brow. I went from swollen eyelids to under eye bags. What is going on? (photo)

I do not think that Botox is the reason for your eye bags. I would followup with your treating physician to discuss further management. 

Great question, thank you!  While Botox will diffuse a small amount after injection, it would be unlikely that it would cause bags under your eyes.  With the history of the swollen eyelids and response to Benadryl and steroids, it seems more consistent with an allergy.  I would recommend returning to your injector for further evaluation and also speak with your primary care provider if this does not improve.  Thanks again for the question.  Best wishes, Dr. Lindsay J Sturm

Using Botox in upper third of face should not effect your lower eyelids. I would think more about allergy, etc. If not better soon, see your primary care doctor.