Yellow discoloration of the skin, especially on the palms and the soles, but not of the sclera and mucous membranes (i.e., oral cavity) is due to carotenemia—a harmless condition[4] important to differentiate from jaundice. Other things that can cause similar discoloration include as a side effect to the use of drug mepacrine or excessive exposure to phenols.
Carotenemia or carotenaemia (xanthaemia) is the presence of the orange pigment carotene in the blood from excessive intake of carrots or other vegetables containing the pigment resulting in increased serum carotenoids
sometimes i have whitening and kind-of yellowing of the only surface of
my tongue but always normal sclera.