Hi
I have a seven month old jack russell cross pup. I ve given her flea treatment, one that you break and put fluid on neck area. She was ok then I took her to puppy training and she's been biting and chewing on her back just at the base of  her tail.  Ive checked her tail area and all over and I cant see any visible flea signes, but she is black!!
She does chew her tail at the end and chases it which looks funny but it must be really annoying her, I know it would me if something I could reach was iching!!  I did notice that there are some small scab patches almost like ecema, sorry if I spelt it wrong, can anybody throw some light on what might be causing it.
I dont bath her loads, once a month, her foods complete dry, gluetin free and her beddings washed and rised thoroughly, with non biology powder as I have sensitive skin.
Thanks
Noel

possibly blocked anal glands, My boy chews the base of his tail when they are blocked. Or perhaps she needs worming? Best to ask the vet.