Lorry tells us that grayness of one side only is sometimes occasioned by severe headache.
Hagedorn has known the beard to be black in one place and white in another.

Brandis mentions the hair becoming white on one side of the face while it continued of its former color on the other.

Rayer quotes cases of canities of the whole of one side of the body.
Richelot observed white mottling of hair in a girl sick with chlorosis.
The whitening extended from the roots to a distance of two inches.

The probable cause was a temporary alteration of the pigment-forming function.

When the chlorosis was cured the natural color returned.
Paullini and Riedlin, as well as the Ephemerides, speak of different colored hair in the same head, and it is not at all rare to see individuals with an anomalously colored patch of hair on the head.