At Pet Dermatology Clinic, we specialize in the diagnosis and treatment of all diseases of the nails, skin, and ears in dogs and cats: 

Why does my pet keep getting skin infections?

The short answer to this question is that the underlying problem is not controlled.  The most common reason for pets to have recurrent skin infections is because the skin is inflamed due to allergic dermatitis, but there are many other reasons.  If your pet is itchy with infections, see here.