A swollen side of a cat’s face may be due to trauma, insect bites or allergies. First, check the cat’s face to see if there is any trauma or other abnormal reactions. If the situation is serious, you need to send the cat to a pet hospital for examination in time. Avoid risk to life. Usually, be careful not to let your cat come into contact with things that contain allergenic substances, and do not give your cat random food to avoid cat allergies.