A melanistic mask (also referred to as a mask or masking) is a dog coat pattern that gives the appearance of a mask on the dog's face. The hairs on the muzzle, and sometimes entire face or ears, are colored by eumelanin instead of pheomelanin pigment. Eumelanin is typically black, but may instead be brown, dark gray, or light gray-brown. Pheomelanin ranges in color from pale cream to mahogany. The trait is caused by M264V (E^M), a completely dominant allele (form) of the melanocortin 1 receptor gene.

Appearance

At minimum, a melanistic mask will appear on the muzzle, and may also be visible on the eartips, entire ears, or entire face. Hairs in those areas will be colored by eumelanin instead of pheomelanin pigment, making it look as though the dog has a mask on its face. Eumelanin is usually black, but may instead be liver (also known as chocolate; dark brown), blue (also known as slate; dark grey), or isabella (also known as lilac; light grey-brown); accordingly, a mask may be any of these colors. Pheomelanin occurs in shades of red ranging from ivory to mahogany, which include cream, gold, and tan.