Chihuahua dogs do not require any special needs. They have the same nutritional needs as other dogs in ratio to their size. The only thing that sets them apart from other breeds is that they don't need a great deal of exercise.
They need to be careful to not get kicked in the head with their constant yapping. Haha jk, but they are yappy. Google "health problems associated with Chihuahuas". It should come up with a multitude of info for you.