To understand this, we must first look to the element of pigmented VS non-pigmented skin. With canines, if the skin holds
In MOST cases, when a Maltese puppy or dog has skin that is turning black, it is a matter of these pigmented areas - whether these be little freckled areas or large patches that were previously lemon or tan - having a change from the lighter color to the darker black color.
Therefore, it is not usually a matter of non-pigmented (white) skin suddenly changing to black; it is instead lemon or tan (that you may have never noticed due to it being very light) already pigmented skin darkening to a black.
And if this happens, it generally occurs as a Maltese matures:
This can happen at any age; a young puppy may develop black spots or an older, senior dog may begin to develop them. Though, in general, it is owners of 1 to 2 year old Maltese dogs that begin to notice this change.
In many cases, it is first noticed during bathing
when the coat is wet and can be quite alarming if an owner does not know that it (in most cases) is not terribly uncommon (but can be prevented or reversed).
Black skin in the show ring:
In regard to skin under the coat developing a black spotting, this element is neither faulted nor preferred in most show arenas; though some feel that black skin pigmentation (that is not due to any sort of health issue) is a good sign of strong pigmentation that only serves to enhance the desirable black points and halos as mentioned above.
An example of how this may work, is that some owners/ handlers may (dishonestly) darken the eye rims with liner and while a professional judge can quickly spot this, pushing the hair aside on the back part and seeing black pigmentation assists to confirm and quantify the existence of true, black points.
There are two main elements that can cause this to happen:
If a Maltese does not have a medical issue (more ahead), the blackening of the skin is often due to 1 of 2 things:
Black skin pigmentation is a trait (just like size
, bone structure, etc.) that is passed down. Traits can be passed down from up to 5 generations back. And, traits can skip generations and this is something to keep in mind when a puppy has traits that neither dam nor sire possesses.
2- Sun exposure.
Exposure to the sun often causes darker pigmentation. In fact, it is not uncommon for a Maltese dog's nose to fade a bit during darker winter months only to darken again in the summer.
Along these lines is the element that being outside - or even laying in a sun-soaked room - can cause black spots to start appearing. These can be anywhere, but are often seen on the stomach.
Please note that if this trait is present and strong in a Maltese dog, even without sun exposure, it is going to emerge. If a Maltese is predisposed to black pigmented skin, this will develop regardless of outside elements.