The most common reasons for itchy skin in dogs include skin infections, microscopic skin parasites such as fleas, scabies or demodex mites, food
allergy, or pollen/dust allergies.
Dogs with fleas or allergies commonly scratch and traumatize themselves, creating a secondary bacterial skin infection/rash that makes the itch worse, and this is something that needs veterinary care. If skin infection is present, it is treated with antibiotics for 3-4 weeks and mild antibacterial shampoos.