Quite possibly, that is your dog's mature skin color. Dogs, just like people, have varying skin colorations. If you think there is something wrong with the dog, however, by all means, take it to a vet and have it checked out.
http://www.helium.com/items/597008-why-do-some-jewelry-metals-turn-skin-green
This could be a normal pigmentation change in some dogs, particularly those with darker fur. However, if there are sudden changes in the nipples or skin such as redness, swelling, discharge, or irritation, it is best to have a veterinarian examine the dog to rule out any underlying health concerns such as infections or hormonal imbalances.
about 10-15 lbs
Anything that has teeth can bite.
The skin of a banana turns brown or black because the skin is very sensitive and when it is kept in cold temperatures... the skin begins to low its quality, therefore turning it darker.
Chihuahas are themselves a dog breed. Perhaps you mean if they belong to the small, medium or large dogs' categories? If so, then Chihuahas are one of the small breeds.
Maybe it's because you have very dirty eyebrows
How would I know silly. Chihuahas should'nt wear clothes!
No you can not get black skin
Because the Yersinia pestis bacteria forms back boils on the surface of the skin. Look at the picture at the link below to answer your question. Internal bleeding also cause blood to pool under the skin, turning it black.
yes tigers skin is black
take your dog to the vet.