Hair follicle inflammation from staph bacteria causes pustules, crusty patches and hair loss most often on the chin, muzzle or chest of dogs.  

Overgrowth of yeast on moist folds of skin leads to intense itching, redness, odor and greasy brown patches typically on paws, ears and armpits.

Allergic reactions, mites, fleas or underlying problems make dogs lick and bite one area so much it becomes a rapidly spreading hot spot infection.  

Ringworm fungus on dogs creates round, bald patches and scaly skin often passed between cats, humans and other pets in close contact.

Microscopic mites like sarcoptes and demodex burrow in the skin leading to intense itching, hair loss and thickened skin lesions transmitting easily between dogs.  

Severe allergic reaction to flea or tick bites results in red, oozing bumps, papules, inflamed skin and hair loss typically starting at base of tail.

Bacterial organisms like Staphylococcus and Streptococcus infect hair follicles and damaged skin causing pustules, itching and fur loss.