Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that your fellow Boots is miserably itchy and cannot seem to settle today.
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 today, but a sudden onset of symptoms like this often comes along with fleas, cheyletiella mites or sarcoptes mites.
Even if you don't see fleas I do recommend using protection, especially during the spring summer and fall months. Flea bite allergy is 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
. Unfortunately even after the fleas are gone the allergic reaction can continue for weeks and I will discuss controlling that reaction below.
Other allergens can be inhaled (like grass pollen, dust mites or molds), but they don't often cause such a sudden onset of itching, they seem to cause a slower onset of symptoms.
You can use a combination of antihistamines and high doses of omega-3 fatty acids to help control the symptoms of flea allergy, and they help with inhaled allergies as well. In combination fatty acids and antihistamines work synergistically, much better than either one alone.
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 of body weight 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 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.
OR 5) Zyrtec (Cetirizine hydrochloride) at 1/2 mg per pound of body weight orally every 24 hours. That would be one 10mg tablet per 20 pounds of body weight. Make sure it is NOT the formulation with a decongestant (such as Zyrtec-D) because dogs cannot tolerate decongestants.
Some dogs do better on one antihistamine rather than another. Give the one you pick a 5-7 day trial 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 high end of the dosing schedule for your pup's weight. I recommend a 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 an 80 pound dog could take 1600mg of EPA per day.
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. Do not bathe your fellow for 2 to 3 days before or after applying flea control products or the bath will interfere with the product's efficacy.
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. Another option is a brand new drug called Apoquel (generic name oclacitinib) which interferes with the allergic pathway. It works very quickly to stop the symptoms of an allergy. Most dogs are reported to be much more comfortable in a day or so. Unfortunately it is on backorder now due to overwhelming demand, but it is something to keep in mind for the future if he continues to have trouble.
If you are interested discuss these medications with your veterinarian as they are prescription products.
Another option if this becomes a long term problem for him and you are interested in better control, is trying immunotherapy. Your fellow would need to be tested to determine exactly what he is allergic to, and then he is given small amounts of the allergen to build up his tolerance to it, increasing the amount of allergen in the injection incrementally so that his immune system no longer responds to it. This isn't a quick fix, it takes time to slowly build up their tolerance and as he develops new allergens things may need to be added, but it is an option.
If it's been a while since his last exam parasites like cheyletiella, demodex or sarcoptes mites should be looked for by your veterinarian as well if he isn't improving as they can lead to very itchy skin.
Please let me know if you have any further questions.