It is not uncommon for the nose on a maltese to lose some of its pigment
during the winter. Sunshine and vitamin E are especially good in helping
maintain good dark pigment. It is also common for a Maltese to loose some
pigment when they go through heat and for sometime thereafter. However,
pigment (nose color), eye rims, etc. is all genetic. Those of us with show
dogs many times breed to enhance characteristics such as this, for example
most of my Maltese have genetic lines with strong pigment behind them and
rarely do I ever have a Maltese loose pigment in the winter or as a result
of their season.
Sunlight will definitely help -- we routinely "sit" show dogs in the sun
(kind of like suntanning) to develop good dark pigment. Kelp added to their
diets has also been shown to help develop good strong pigment.
Bobbie Linden - Bhe-Jei Maltese