Hello, my name is***** and I have over 20 years of experience as a veterinarian.
I'm sorry to hear about your fellow Jager's dry, scaly patches on his belly and I understand your concern for him.
From your pictures this is likely a superficial infection of the skin called staph dermatitis.
It is caused by normal skin bacteria getting introduced under the skin by the dog scratching, licking
or chewing at itchy skin or some sort of allergic reaction to something.
By the time we see a rash they generally need oral antibiotics but it seems that he is improving and there are some things we can try at home to help him heal completely.
Clip the area around and over the rash very short and use a solution mix of Betadine solution and warm water, made to look like weak tea, and clean the affected areas twice daily. This is an antibacterial and will dry the lesions out to allow them to heal. It does stain horribly though so you probably want to do this outside or in a laundry sink. Another option is cleaning the area with chlorhexidene shampoo and warm water, then rinsing and patting the area dry.
If he is licking the area then I recommend placing an Elizabethan collar on him as the more he licks the worse the rash will get. It doesn't sound like this is the case with him.
If his rash isn't much better after 3 to 4 days of treatment he will likely need to see his veterinarian for oral antibiotics.
Long term if this becomes a repeated problem for him to prevent the rash from returning we need to address the underlying cause. Allergies are the most common cause of this skin rash. Dogs that have one allergy often develop several with time. The effect of multiple allergies aren't additive, they actually compound one another.
Even if you don't see fleas I do recommend using protection. They are the most common allergen and it only takes one bite a month to make an allergic dog scratch so I recommend using flea prevention even if you never see one again. Frontline Plus, Advantage II or Advantix are excellent. Don't use over the counter products, especially Hartz or Sargents, as most are ineffective if not toxic
Other allergens can be inhaled (like grass pollen, dust mites or molds).
You can use a combination of antihistamines and high doses of omega-3 fatty acids to help with the symptoms of inhaled allergies and flea allergy. In combination fatty acids and antihistamines work synergistically, much better than either one alone. If his symptoms worsen seasonally I would think that inhaled allergens are a part of his problem.
You can try:
1)Benadryl (diphenhydramine only don't use the combination products with acetaminophen or decongestants as they can be toxic for dogs) at 1mg to 2mg per pound or one 25mg capsule per 15 to 25 pounds of body weight orally every 8 hours.
OR 2)Claritin (loratidine) at 5mg per 25 pounds of body weight dog once or twice daily.
OR 3)Hydroxyzine at 1mg per pound of body weight orally every 8 hours.
OR 4) Chlorpheniramine at 4mg to 8mg per dog once or twice daily.
Some dogs do better on one antihistamine rather than another. Pick one, give it a week trial and if it isn't working try another. Be aware that antihistamines can cause sleepiness or hyperactivity in some dogs. These side effects do wear off with repeated use.
Omega-3 fatty acids are fish oil products. 3V by DVM or Derm Caps ES are good brand name products. Use the high end of the dosing schedule for your pup's weight. I recommend a fatty acid dose based upon the EPA portion (eicosapentanoic acid) of the supplement as if we do that the rest of the supplement will be properly balanced. Give him 20mg of EPA per pound of body weight per day. For example a 75 pound dog could take 1500mg of EPA per day.
Antihistamines and omega-3 fatty acids work synergistically, better than either one alone.
You may choose to use an omega 3 fatty acid alone if he doesn't seem itchy simply to support skin health and healing.
Please let me know if you have any further questions.