Plastic Dish Dermatitis = alteration of Pigment
Plastic dish dermatitis occurs when the plastic chemical p-benzylhydroquinone inhibits melanin synthesis, altering a dogís nose and lip colour. In addition to losing pigment, skin damaged by plastic can become irritated or inflamed.
This is a localised form of depigmentation that affects noses and lips. It is caused by drinking and eating out of plastic and rubber dishes that contain the said chemical - this chemical is absorbed through the skin - Simple solution is to change to glass, ceramic or stainless steel bowls.
Why plastic bowls are still on the market is beyond me!
Of course there are dogs born with a genetic fault and have pale to pink noses (patched sometimes) from the off but for those that have good black pigment, protect from fading by changing the bowls if you already have not done so.