These are images of two cats (6 and 10 years old) who live in the same house and developed the same skin condition, with crusting, bleeding, and intense itching on the front aspect of the ears and nose:
At first, one might think that these cats had something contagious, since they are not litter mates, and they developed the same lesions at the same time, but these lesions are classic (almost textbook) for mosquito bite hypersensitivity.
As a little extra history, these cats are indoor only, and weren’t on any flea and tick prevention, but live in Indonesia where it was high mosquito season. These cats required treatment with steroids for the hypersensitivity reaction, and most importantly mosquito control (fogging around the house, and flea prevention with repellent activity).
While this appearance is classic for this condition, there are several other conditions that can cause itching, hair loss and scabbing such as this in cats and dogs, so if you see lesions like this in your dog or cat, please consult your veterinarian or veterinary dermatologist for diagnosis and treatment.