My cat has a red bump on her by her ear. I noticed it about a week ago and tried some hydrogen peroxide to clean it. The bump is red, round, and a bit scabby. She typically has allergies each season, so I was thinking it might be that, but she has never had any bumps before. Nothing has changed in her diet or lifestyle. She is strictly an indoor cat. We have another cat and she has no bumps, so whatever it is, I do not think it is contagious. Her behavior is pretty normal, I don't even notice her scratching the bump.

Any advice would be great!