I've been diagnosed w/ angioedema. i didn't tell my derm i've been taking 3 hydrocodone/day for years. could it be the cause?

Yes: Opiates can release histamine although most of the time you would end up with hives only. On the other hand there may be many other potential causes for angioedema and perhaps an allergist can help you sort this out better. In the future, hide your medication history from your doctor at your own risk.

Maybe: Hydrocodone can cause release of histamine and swelling. It is unlikely that you are experiencing swelling from hydrocodone after years of taking it but it is a possibility. To eliminate hyrdrocodone as a suspect it would be necessary to stop it for a about a week. I suspect that may not be easy for you so in the meantime have your doctor continue to evaluate you for other possibilities.

Almost any: Medication can cause hives and angioedema. Hydrocodone not a common one. Have you have problems with swollen of your throat? It's a more severe cause call hereditary angioedema. Do a cause relationship check. Every time you develop the hives review what you ate, drink, doing, wearing, using like make up, shampoo, soap etc.