Sudden swelling of the face, lips, ears, and eyelids can be caused by a hivelike allergic reaction called urticaria. The cat’s head may appear strangely out of proportion to her body, and the eyes may be swollen shut. Common causes are food allergy, contact and inhalation allergy, and the bites and stings of insects. Swelling may appear as much as 20 minutes after exposure to the allergen.
Treatment: Most reactions subside in three to four hours. Cool compresses may relieve some discomfort. Your veterinarian may choose to administer adrenaline or an antihistamine. You should try to find out what caused the allergic reaction so you can prevent your cat from coming into contact with that allergen again.
The most common behavior problem reported by pet parents of cats is inappropriate elimination. It’s estimated that 10% of all cats will eliminate outside their litter box at some point in their lives. Quite a few of these cats have issues with some characteristic of their litter box (please see our article on Litter Box Problems for more information on litter box problems), but approximately 30% don’t have litter box problems at all. These cats are urine marking, and urine marking isn’t a litter...
The addition of wheezing, respiratory distress, vomiting, or diarrhea indicates a potentially serious allergic reaction. Snakebite is another possibility. Seek immediate veterinary attention.
Head and Neck Abscesses
Head and neck abscesses appear suddenly and are accompanied by fever. They are extremely tender and may give a lopsided look to the head, face, or neck. Opening the mouth causes extreme pain in some cases. These cats refuse to eat or drink. Many have a high fever.
WebMD Veterinary Reference from "Cat Owner's Home Veterinary Handbook"