First I want you to relax and understand that there are very few skin conditions of a pet dog that could be contagious to us humans!
Any kind of raised bump or blister like appearance on the chin of a pet dog, is usually due to a condition called folliculitis, or inflammation of the hair follicles. This condition is common in pets that are suscept to staph infections, that have demodectic or sarcoptic mange mites, and that have allergies to plastic and other feeding bowls that their chin may come into contact with on a regular basis.
Diagnosis of the exact problem should be done by your veterinarian. A procedure called a skin scrape will be done on your pet's affected areas of chin and a sample of cells and debris from your pet's skin will be visualized microscopically to assess for the presence of mites or bacterial organisms.
Treatment for folliculitis often entails antibiotics, usage of stainless steel (hypoallergenic) feeding bowls, antiinflammatories, and any indicated mite therapies.
Of the causes of folliculitis, the only contagious one to humans if the Sarcoptic Mange mite. Generally, pets affected with this mite are Extremely Itchy!! These mites can be difficult to find on a routine skin scrape, so your vet may suggest treatment for this mite EVEN if the skin scrape comes up negative!
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Best wishes to your and your pet, Dr. Smith