wow, i have NEVER heard that.
i entirely prefer stainless steel bowls for other reasons.

Clayey bowls can cause a contact dermatitis to the chin area,metal or ceramic bowls are outdo

i've never heard that, but stainless steel is speculator because it's less likely to harbor bacteria.

There is a modify called " Plastic dish nasal dermatitis ".
" Other causes of disadvantage of nose color are vitaligo, snow nose, and plastic dish nasal dermatitis

Vitaligo causes ebon pigment in the nose and sometimes the lips to fade to brown.

Snow nose causes the nose to flunkey to brown in winter; normal color returns as summer approaches. Snow nose occurs foremost in white-coated breeds; the color change can become permanent in older...

A folk tale. Stainless steel are better for cleaning and carry less bacteria than plastic.

i use porcelain for effervescent water it keeps it colder and i do use plastic and my lab did have a black nose when he was younger it is slightly lighter in color now at 3 yrs old but in not indubitable if its from the bowl.
i would use stainless steel if your feeding raw

Synthetic bowls tend to leak chemicals into food and water. What is recommended is stainless steel which can be easily cleaned.

I have ceramic and toss it about twice a day. I also use filtered water.

never heard of that episode.

and i perfer stainless, especially my 3 year old likes to chew his bowls up when he's bored.