Delayed or prolonged reaction to wasp stings

Back in August, I was stung on the ankle by a wasp. I had an immediate reaction where my foot turned bright red from the ankle down to my toes and from the arch of my foot halfway across the top of my foot. This took almost two weeks to resolve itself. Benadryl did not help.

On Wednesday morning of this week, I was stung by a wasp just below the knuckle on my left hand. I felt pain and burning for a few minutes and then seemed fine. There was no welt or redness. When  I woke up this morning (more than 48 hours later), I noticed significant redness and swelling from the tip of my thumb down to my wrist and across from near the palm to the bone to the pointer finger.

I took an antihistamine late this morning, but the swelling continued into my wrist. The red area is hot to the touch. There is no itching, but it does feel uncomfortable. My throat does feel a bit thick, but my blood pressure and hear rate are fine. I do have a headache. I spoke to my doctor about another issue and mentioned this to him and he has put me on antibiotics for a week.

It's been years since I have been stung by bees or wasps and now I have been stung twice within a short period of time. Is it possible that I am developing an allergic reaction to stings? I am on Coumadin for DVT. Could this have anything to do with the way I am responding?