Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you.
This sounds like Allie has experienced some sort of trauma. If she is an outdoor cat, which I assume, then the most common trauma to cause this is a cat fight and claw/scratch which has become seriously infected, an abscess. This is an issue that probably not going to be treatable without an antibiotic. That means you really should consider having her seen by her veterinarian. If you have trouble getting in to a clinic, then you could have a mobile vet visit you; you could try containing her to an area and have the vet visit. There is an injectable antibiotic she could be given so you do not have to actually give her something by mouth.
Until you have her seen by her veterinarian, the only thing you can do is try to flush/cleanse the area as best possible.These are very painful and please be cautious not to get injured doing this. If you do nothing and elect to watch this, if there is a bit swelling it will probably rupture which could then lead to a fairly large wound on the side of her head, and this is much more difficult to treat.
There isn't anything you can buy over-the-counter to put in her food
or treat her from afar, unfortunately.
Alternatively, maybe this is not an abscess or fight-wound. This could be a tumor at her age, which is not good. This would not carry a good prognosis for long-term.
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