Could also be a sign of fever. Lamoni would sometimes come in panting. Usually this was when he needed a "rear end alignment". Long hair, runny stools ... well you get the idea. Sometimes he was so bad even he could not stand himself.

We thought that was the cause of the panting. He would also pant if he came in from eating something disgusting like a slug, bug, or other nasty thing that crawled in throught the cracks in the garage wall.

Tiurns out that the bad smell of himself was giving him an anxiety problem and that was causing a fever. Now cats will spike high temeratures just on a sudden noise. Sustained for very long and they can't cool down the inside well.

If this last more than, say, 48 hours or the ears are hot to the touch, then go to the vet for a check up.