[HannaBanana]

I dont use plastic bowls just because they can be brothels for parasite and bacteria.

Even stainless steel bowls can cause some staining or itchyness under the chin (my dog has it all the time).   Try using some apple cider vinegar on the chin to see if it helps.    Thats my advice besides using a topical steroid.  

I am in the middle of battling seasonal allergies and its a nightmare!!!

 

[HannaBanana]

Also it could be a form of Canine acne.  That is very common area for that

 

[HannaBanana]

Just came back from the vet with Hanna.  She has constant allergies.  Vet said pollen is bad this time of year or she could have a reaction to bug or certain treat.

So we put her on a mile steriod to clear up the rashes.   So your not the only one