Thank you for the reply and I am sorry that you have had to wait for a response. I must have logged off just before you replied.
I am very concerned that Toby is manifesting early signs of a condition called atopic dermatitis. Atopic dermatitis (AD) or eczema is a long-lasting (chronic) condition that causes itchy inflammation of the skin and ears. It may affect any area, but it is usually affects the face, feet, armpits, trunk, and abdomen. It may be persistent or it may flare periodically and then subside. These can make a dog's skin itch and there may or may not be other skin lesions visible. Itching problems in pets can be difficult to diagnose and the history and response to medications tried are a very important part of figuring out the cause. I know that he is young and you don't have a history of recurrent ear and skin problems yet, but when I see a young dog with a history of 2 ear infections already and now a pyoderma (skin infection), I will definitely warn the owner that this may be a sign of things to come.
Animals with AD have two main problems. The first is an abnormal skin surface (barrier) which leads to sensitive skin. The second is an overactive immune system that reacts to a variety of flare factors. Recognized flare factors include: dry skin, food allergens, parasites (fleas), infection (bacterial or yeast), and environmental allergens, like dust, pollen, molds, etc . When a flare occurs, your pet will itch more and may develop red, flaky, and/or infected skin or ears, as these areas are then invaded by bacteria or yeast. When these bacteria or yeast live there for a long time, the skin can develop secondary lesions and even become blackened and thickened. These secondary infections require a specific treatment to resolve and is separate from therapy to manage the AD. A test called a skin cytology can be done to look for these organisms that cause infection. There are other things to look for on the skin that can make a dog itch and cause skin changes like mange mites and ringworm. Mange mites, particularly demodex, can be a problem in young dogs, so I wuld definitely request your vet to do a skin scraping of those lesions on his belly.
Since he is young, and food allergy has to be a consideration, I would not be making a lot of food changes at this time. A true "elimination diet" to prove a food allergy requires feeding him something he has never seen before. If you offer too many alternatives before a food trial, you may be setting him up for trial failure. My suggestion at this time is to have your vet evaluate his current lesions. If there is bacterial infection, as it sounds like there is, get a skin scrape to rule out demodex and treat with the appropriate antibiotic (oral or topical). Depending or response to treatment and seasonality of his itch or skin lesions, it can be decided if food or environmental allergen trigger needs to be ruled out next.
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.
My posted replies are for general education only and not meant as a diagnosis. Only after a thorough veterinary examination can a diagnosis for your pet be made and specific treatments be advised or medications be prescribed.