patch of hair coming out

Question
a few weeks ago, my dog came home from the kennel freshly bathed. i noticed a clump on his side, i tried looking throught the hair but couldn't see any thing. it's been 3 weeks, and last night i looked again, and a bunch of hair pulled off very easily, patches of hair on that section... his skin looked really dry/white. he has been off of allergy pills for almost a yr. after being on them for 6 yrs. (we moved to Ca. and his paws cleared up instantly) he's 12/13 yrs old jack russell/beagle. what should i do?

Answer
If it's been three weeks, then the hair has come off of a patch of skin that was injured somehow. He could have been cut, burned, chemically or otherwise, or razor burned if he was trimmed. It could have been a large matt as well that was tangled (but they should have removed it). It could have pulled out and irritated the skin.

Since it's been three weeks it's hard to know what it could have been without seeing it.
If you continue to see hair come out or in different spots, then have your vet look at is as soon as you see it.