Hi there, this is Dr Linda, a small animal vet with 10 years of clinical experience.
I'm sorry to hear about this cat's ongoing issues and thank you for trying to help them!
Constant ear rubbing like this could have several causes including:
- A chronic bacterial or yeast infection
- Ear polyps
- A squamous cell carcinoma (particularly if she has white ears and the ears are scabby)
- Allergies (particularly if she itches elsewhere)
- Ear mites
Ideally she would be brought to a vet for something like this, so we can ensure she gets the right tretament. If she has not been neutered, this would be a good opportunity for this.
As you, with ferals this can mean humanely trapping them and perhaps sedating them.
As putting drops in her ear likely isn't an option while awake, the vet can instil a long-lasting drop in her ears if she does have an infection.
They can also clean the ears and remove any debris or foreign matters.
If irritated and inflamed, she may benefit from a steroid injection too.
The vet can prescibe a drop containing Imidacloprid which can help treat ear mites as well as fleas.