Obesity
Overfeeding is a risk to Chihuahuas' health and can ultimately lead to diabetes and shortened lifespan. Care must be taken to provide them with a diet that provides adequate nutrition and matches their activity level. Overweight Chihuahuas are prone to joint injuries, tracheal collapse, chronic bronchitis, and shortened life span.
Genetic Predispositions
Chihuahuas are prone to hydrocephalus, a condition characterized by excessive accumulation of fluid in the brain. Chihuahua puppies exhibiting hydrocephalus usually have patchy skull plates rather than a solid bone, and typically are lethargic and do not grow at the same pace as their siblings.
Additionally, Chihuahuas are known for moleras, a soft spot in their skulls. Chihuahuas are the only breed of dog to be born with an incomplete skull. The molera does fill in with age, but great care needs to be taken during the first six months until the skull is fully formed.
Other Health Tendencies
Chihuahuas are prone to eye infections due to their large, round, protruding eyes and their relatively low ground clearance. Chihuahuas also have a tendency to tremble but this is not a health issue, rather it usually the result of the dog being stressed or excited.