Thanks for the query,Bee sting
can cause swelling,
However a you are on coumadin
you need to take extra precautions.
Coumadin is a blood thinner and hence can cause increase in swelling.
There is also a chance of bacterial infection.
Take a course of antibiotics.
Apply an antibacterial cream like mupirocine.
Hot fomentation is also good,
It will reduce the pain and decrease swelling.
Take an anti histamine
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.