The final part of my series on pet allergies covers bacterial allergy, which is an over-reaction of the dog or cat's immune system to normal skin bacteria. A bacterial problem usually appears as a secondary infection following another type of skin infection. The most common organism is Staphylococci, which is not contagious to humans or other pets.
Symptoms are red and ulcerated skin, itchy yellow pustules, turning into dry crusty areas as the problem continues, along with hair loss and odor. It can look very much like ringworm, and usually affects the trunk of the pet, but can appear in any area. A bacterial infection is suspected when antibiotics work for a while, but the symptoms return after the antibiotics are stopped, and can be confirmed with an Intradermal Skin Test.
Treatment requires antibiotics to get the disease under control, and following up with desensitization using killed staph bacteria for long term treatment. Washing the pet with antibacterial shampoo such as benzoyl peroxide, and applying antibiotic ointment to dried skin along with antibiotic pills for 3 to 4 weeks is usually prescribed.