I am sorry Rudy is so itchy. The most common reason for dogs to lick their feet and armpits is an allergy, often to things in the environment such as pollens. Sometimes antihistamines help; sometimes you have to try 2 or 3 antihistamines. What have you tried so far?
There is no cure for allergies, yet. If antihistamines do not help, the next step is to try prescription medication such as Temeril P, prednisone, Atopica, and the newest medication that works very well in 80% of dogs, Apoquel.
There are supplements that may help, in combination with histamines: Quercetin, Fish oil, Vitamin E and other antioxidants, Nettles.
Each case is different, and you have to try one thing after another until you find what helps Rudy.
Are you using flea control on him?
Let me know what other questions I can answer.