Cat with blisters on ears?

[Frosty]

I took my kitty in to the vet today, she has a lot of little blisters on her ears. The blisters have been there for more than 2 weeks. I thought they were from ear mites, I knew she had a mite problem so I treated all of the house cats with Ivermectin. The blisters are still there so I took her in. The vet looked and said they were from bug bites. I asked from what since she is strictly indoors. So he checked for mites, she didn't have any. Did a skin scraping to check for other mites, nothing. Checked for fleas, nothing. I asked if it could be sunburn from sitting in the window, he said possible but mot likely. I do have an orange cat that gets little blisters and a raw nose if he escapes outside during the day, he gets sunburn. But his blisters are clear, and this cat (a gray tabby) looks more like little blood blisters if the light is behind her. For now she is going to be on Prednisone and see if that helps, but does anyone have any other ideas? He really thinks it looks like biting gnats got her, but unless they are in my house and just going after her? He did say that I can give her more Ivermectin while on the Prednisone, and recommended that I do a third dose after the one tonight. The blisters were there before the Ivermectin, so they aren't from that...

 

[Attila the Hen]

I've had a lot of cats and probably know more about them than chickens. I havn't seen blisters on the ears but I have seen scabby areas that I suspect are bug bites. The first thing I thought of were stick fleas but I am not sure you get them where you are. They are tiny bugs we got in FL that are hard to pull off. Not sure what else it could be and I wouldn't worry unless the cat seems disturbed. My general rule of thumb is if anyone (dogs and cats) stop eating then I take notice.