Dark Hair Spots on Chihuahua

Question
I have a 4-year-old, tri-colored Chihuahua.  She is current on her vaccinations and has been spayed. She is mostly an indoor dog, although in warm weather she likes to sit outside for hours at a time. Most of her neck, front legs, back-end and hind legs are solid white, but recently over the past 2-4 months some black spots have started to appear.  The spots are in her hair, almost as if the pigmentation of the hair is changing.  When I run my hand through the hair, you can see that the hairs are entirely black. I understand that a dog's coloring changes as they age, but I've never had a dog go from a solid color to having spots so I'm a bit concerned. Is this normal or should I schedule a vet appointment?

Answer
Well first of all, white dogs can get two things: sunburned hair and skin, and skin cancer.

White animals, both cats and dogs, are susceptible to this and 4 years of age is the age that some dogs and cats will start getting spots of pigmentation that may or may not become cancerous.

I don't know where you live but I live in the Sierra Nevadas and white cats here get ear cancers on their ears quite commonly. White dogs are prone to skin cancers around the eyes (if the hair is white and skin is pink), the ears and the nose. We also see it along the back and neck and top of the head.

However, dogs can and do get pigment spots from just sitting in the sun that are harmless. Red cats start to get light brown freckles all over their mouth, eyes and sometimes the nose areas around the age of 4-5. It can be alarming to see none one day then suddenly there are plenty of them.

I would have the vet look at them only to be sure that they are NOT cancers. Melanoma is the cancer that white animals get and it's not a good thing.

She is probably just fine, but your vet may suggest sunscreen for her.