Hello, my name isXXXXX and I have over 20 years of experience as a veterinarian.
I am so sorry to hear about poor Copper, he sounds miserable.
Allergies are the most common cause of itchy skin and can give him a skin crawling, all over itchy type effect which many dogs find irritating.
I'll give you an allergy rundown of likely causes for skin troubles. He may have more than one allergy given how symptomatic he is now. 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, if only during the spring,
summer and early fall months. 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 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) and you can use a combination of antihistamines and high doses of omega-3 fatty acids to help with those (they also help with the symptoms of 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 decongestants and acetaminophen as they can be toxic) at 1mg to 2mg per pound or one 25mg capsule per 25 pounds of dog orally every 8 hours.
OR 2)Claritin (loratidine) at 5mg per 25 pound dog once or twice daily. You've been giving that at a higher then normal dose and it doesn't sound like it's helping much so I would recommend trying another antihistamine from my list.
OR 3)Hydroxyzine at 1mg per pound 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.
You'll have to try one for 7 to days and see if it works, and if it isn't working try another. Be aware 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 highest end of the dosing schedule for your pup's weight. The low end is for prevention but he needs more if he is already so itchy.
Cool water baths with an oatmeal shampoo or chlorhexiderm shampoo (which is antibacterial and antifungal) and a conditioner with an antihistamine may help. The water rinses off allergens and the cool temperature soothes itchy skin.
Food allergy is very possible with him as food allergic dogs often have very itchy faces and paws. Dogs can develop allergies to any protein or carbohydrate so even
if he is only fed one thing that can be what he is allergic to. Dogs with food allergies tend to lick and scratch their paws, face and ears the most, but any of the "allergy reactive areas" can be affected. You could try a true hypoallergenic diet like Hills z/d or Purina Veterinary Diets HA. No treats, flavored medication or bones while on the diet and it must be used for a least 12 to 16 weeks to see the full effects. Most owners see some improvement in 6 to 8 weeks. In a dog that I truly believe has food allergies I recommend going to prescription foods. The trouble with "limited ingredient" or "low allergy" pet store brands is that the same machinery is used on multiple lots of food without sterilization cleaning in between. So for example even if a food says it has salmon and rice if the previous batch had beef and corn then you will get traces of those ingredients in your bag of food. Not a big deal if your dog isn't allergic but a waste of money thinking that the food was hypoallergenic and not good for your dog if those happen to be allergens for your dog. The veterinary brand
true hypoallergenic foods are more expensive because it isn't cheap to thoroughly
remove all traces of a previous food mixture from the machines used to process
Generally what I recommend is trying to clear the skin and ears and then adding
one food item (chicken, beef, corn wheat etc) every month to see what they react to. Then we can find a regular food to try. I do tend to stick with Purina brands or Nature's Recipe as I find those rarely if ever have cross contamination. Purina Pro Plan Turkey and Barley or Nature's Recipe Vegetarian or Venison are pretty good products. I know that this isn't easy from personal experience (my dog is allergic to wheat) and it is time consuming, but worth it.
Cortisone ointment applied to the very itchy places (as long as they aren't raw) twice daily may help as well if needed. Some sprays have alcohol which can be painful on raw skin and lead to more inflammation. I don't like oral steroids but topicals directed at the problem areas can be very helpful and are less likely to cause side effects. In some cases we do need oral steroids for a short time but I try antihistamines and omega 3's first.
Another option if the antihistamines and omega 3's aren't enough is a product called Atopica. It suppresses the immune system a bit so it decreases allergic symptoms but it doesn't have as many harmful side effects as systemic steroids. If you are interested discuss this medication with your veterinarian as it is a prescription.
If it's been a while since his last exam parasites like cheyletiella, demodex or sarcoptes should be looked for as well if he isn't improving as they lead to very itchy skin.
Please let me know if you have any further questions.