Everything we see or measure from an animal (a dog) is the sum of the genetic predisposition of an animal as well as numerous environmental influences. For breeding, only the genetic predisposition is important. Our own measurements and the performance of an animal are not enough to accurately predict the genetic predisposition of an animal.
The following are some more common health issues in dogs, in general and not considered specific to the Cavalier King Charles Spaniel, nor considered inherited in the breed at this time. Allergies: like people dogs can have allergies. They can manifest in different ways, some dogs may have skin problems, others may have itchy eyes