I think it is quite common to have red eyes in photos especially when we are taking pictures in the dark light environment. Red eye may occur when photographic flash is very close to the camera lens. Red eye will appear in the eyes of humans and animals in the night, because they don't have tapetum lucidum and eyeshine. if the animal have a tapetum lucidum, this may rarely happen.
Red eye looks unnatural. There are some ways to avoid it or remove it. They are easy and convenient in fixing this problem. You can get a good photo from a camera with the flash built in. it will make the environment more bright. Or when you are taking the picture, you can ask people to look at your shoulder. However, if the picture is there, you can ask the professionals to modify the pictures. Usually they will finish it on computer.