Cats are masters of masking discomfort, and sometimes it’s not so obvious that they may not be feeling well. Since cats can’t communicate their symptoms verbally, understanding their body language and behavior is important in detecting illness early.
Of course if you notice visible symptoms like labored breathing, discharge from the eyes or nose, wounds, or swelling of any areas, these are more obvious signs your cat may be ill. Always consult your veterinarian right away if you are concerned.