Dogs suddenly fighting - could one be ill?

[monster]

Hi

I wonder whether anyone can help.

I have two girl Jack Russells who have been together almost 3 years. Generally they get on well, have the ocasssional scrap which is easily forgotten when they are offered a biscult.

The younger one of the had an allergic reaction to something last Wednesday, she was taken to the vets and given some priton, she seemed fine after this although rather quite but still eating and generally alert, they had a scrap on Friday evening which was the first time in a long time but as above it was easily forgotten.

We got home last night after going out for dinner and let them outside, next thing they are having a huge scrap out in the garden, we seperately them and calmed them down, but as soon as they got near each other again they started.

We seperately them overnight and tried again this morning, the younger one gowled as soon as she got near the other one. We decided to take them out for a walk which seemed to work and they were able to be in the same room without attacking each other. However some post came through the door, they both went for it and then started fighting again and we are back to square one.

Has anyone every seems this before, I am thinking the younger one isn't well and is fighting the other one because all she wants to do is play. Have a vets appointment for her at lunch but any suggestions on what this might be would be greatly appreciated.