We share many things in common with our furry friends, one of them unfortunately is allergies. Just like human allergies, dog allergies are a result of an immune system reacting to an allergen, a substance that usually harmless but which in allergic animals causes the immune system to overreact. Commonly the immune system’s irritation is manifested through the skin. Hence, an allergic dog will experience redness, itching, skin infections, and hair loss.