Pulling fur out

Question
I have a male Jack Russell Terrier (2 1/2 years).  Just the other day he started pulling at his fur on his front arms.  His skin is red all the time too.  Its not falling out on its own but I'm having a hard time babysitting him so he won't clear off all his fur that he could reach.  Any ideas of what it could be or what I could do?  He does have fleas which we've also had a hard time getting rid of (tried baths, and sprays but they keep poping up, also is on frontline).  Would that have something to do with this?  He just got his first tennis ball for the first time and ripped all the fuzz off of it.  Is he just looking for something else to chew on?  Thanks for your input.

Answer
When dogs itch their legs it is often an allergy.  Ask your vet to see if allergic dermatitis is possible.  Mange, ringworm and infections are also possible reasons. It could also be a nervous habit called obsessive compulsive disorder.  In a Jack Russell anything nervous in origin can happen!